oh, and cost...
here's a bunch of info I collected when I was doing my search last summer (the pricing info is outdated)

EVO History:
http://www.evotuners.net/forums/f2/l...-history-4376/

EVO Faq:
https://www.evolutionm.net/forums/ev...oking-evo.html

Weight reductions:
http://highboostforum.com/forum/show...duction-thread

More weight info:
http://www.vorshlag.com/tech_evoweights.php


2003 (Evolution) - 3,263lbs ($13,733 average)
Edmunds TMV = $14,167
NADA clean trade-in (100K)= $12,875/$15,650 (Tradein/Retail)
KBB Private Party (100K)= $12,320/$13,220 (Good/Excellent)
5-Speed
7,000RPM redline
235/45/17 wheels/tires
271hp/273lbft
no cruise control
no helical front diff
viscous center diff
mechanical rear diff

5-Speed:
1st: 2.928:1
2nd: 1.950:1
3rd: 1.407:1
4th: 1.031:1
5th: 0.720:1
final: 4.529:1

2004 (Evolution and RS)
Evolution (GSR) - 3,263lbs
Edmunds TMV = $15,489
NADA clean trade-in (100K) = $14,825/$17,650 (Tradein/Retail)
KBB Private Party (100K)= $13,790/$14,790 (Good/Excellent)
5-Speed
271hp/273lbft
Cruise Control?
no helical front diff
Evolution RS - 3,218lbs
Edmunds TMV = $14,002
NADA clean trade-in (100K) = $13,650/$16,425 (Tradein/Retail)
KBB Private Party (100K)= $12,400/$13,350 (Good/Excellent)
helical front limited slip diff
aluminum roof
air conditioning is included
no ABS
no power windows, locks or mirrors; no audio system, no map lamps, less sound deadening
(Urban Jungle package includes power windows, locks and a stereo)
no rear wing

5-Speed:
1st: 2.928:1
2nd: 1.950:1
3rd: 1.407:!
4th: 1.031:1
5th: 0.720:1
final: 4.529:1

2005 (Evolution VIII, MR and RS)
Evolution VIII (GSR) - 3,263lbs
Edmunds TMV = $17,159
NADA clean trade-in (60K) = $16,750/$19,650 (Tradein/Retail)
KBB Private Party (60K)= $18,535/$19,685 (Good/Excellent)
ACD
helical front limited slip diff
5-Speed
276hp/286lbft
larger turbine housing, more boost
Evolution RS - 3,182lbs
Edmunds TMV = $15,574
NADA clean trade-in (60K) = $15,325/$18,125 (Tradein/Retail)
KBB Private Party (60K)= $16,785/$17,845 (Good/Excellent)
ACD
276hp/286lbft
helical front limited slip diff
aluminum roof
air conditioning is included
no ABS
no power windows, locks or mirrors; no audio system, no map lamps, less sound deadening
no rear wing
(Urban Jungle package includes power windows, locks and a stereo)
Evolution MR - 3,277lbs
Edmunds TMV = $18,703
NADA clean trade-in (60K) = $18,150/$21,100 (Tradein/Retail)
KBB Private Party (60K)= $19,545/$20,745 (Good/Excellent)
6-Speed
ACD
276hp/286lbft
helical front diff
Bilstein shocks


2006 (Evolution IX, MR and RS)
http://www.modified.com/roadtests/05..._ix/index.html

Evolution IX (GSR) - 3,263lbs
Edmunds TMV = $19,777
NADA clean trade-in (48K) = $18,100/$21,050 (Tradein/Retail)
KBB Private Party (48K)= $20,610/$21,860 (Good/Excellent)
5-Speed (higher first gear, and lower 3rd-5th)
7,000RPM redline
ACD (active electro hydraulically controlled) center diff
helical front limited slip diff, clutch style rear
286hp/289lbft
larger compressor housing
Variable Valve Timing (MIVEC)
Evolution RS - 3,219lbs
Edmunds TMV = $18,093
NADA clean trade-in (48K) = $16,275/$19,125 (Tradein/Retail)
KBB Private Party (48K)= $18,170/$19,320 (Good/Excellent)
aluminum roof
ACD
air conditioning is included
no ABS
no power windows, locks or mirrors; no audio system, no map lamps, less sound deadening, no trunk lining
no rear wing
no rear wiper
(Urban Jungle package includes power windows, locks and a stereo)
286hp/289lbft
larger compressor housing
Variable Valve Timing (MIVEC)
Evolution MR – 3,285lbs
Edmunds TMV = $21,908
NADA clean trade-in (48K) = $19,625/$22,600 (Tradein/Retai)
KBB Private Party (48K)= $22,135/$23,435 (Good/Excellent)
6-Speed
ACD
helical front limited slip diff
aluminum roof
HID xenon headlights, fog lights, gauge-pack
zero-lift kit (?)
286hp/289lbft
larger compressor housing
Variable Valve Timing (MIVEC)
Evolution GSR SE – 3,294lbs
(Black, Gray or Silver)
Edmunds TMV = $????
ACD
Aluminum Roof
5-Speed
286hp/289lbft
larger compressor housing
Variable Valve Timing (MIVEC)

5-Speed:
1st: 2.785:1
2nd: 1.950:1
3rd: 1.444:1
4th: 1.096:1
5th: 0.761:1
final: 4.529:1

6-Speed:
1st: 2.909:1
2nd: 1.944:1
3rd: 1.434:1
4th: 1.100:1
5th: 0.868:1
6th: 0.693:1
final: 4.583:1

 

I have driven a non-ACD evo VIII since I bought it new in early '04. Since you are coming from a 2.5Rs I don't think you will have much of a transition to the '04 RS.

despite the extra weight of the ACD, I think overall it can provide better and more consistant performance. My biggest complaint with my evo is the application of the torque split compared to EVOs with ACD. With the ACD, the torque split is maintained with the computer. With the EVO, like your impreza, the torque split is maintained by your throttle inputs.

I am not sure how much that will affect you in STU, but in SM I find that it is an issue I need to deal with.

 

I ran an STU Evo9 MR last year.

I have never had the ABS come on during a run unless it was raining, at which point the ABS can brake faster than I can. However I had to be driving poorly to set them off.

The front diff is great, and the ACD is very consistant. The power application is great with it.

As for power, with E85 and the MIVEC, the 9 makes better power. The MIVEC tuned properly will boost faster and have a broader power bad.

 

hmmm, were you on concrete? I get in the abs sometimes when driving my friends EVO XIII, he has a pretty robust brake setup though, maybe too much for the available traction..

thanks for your input chris.

I (the OP) picked up a 2006 GSR late last summer/fall. Found an ok one local with no mods and reasonably low mileage, oh, and no sunroof

been researching and buying STU parts ever since... now we just need to get it all sorted!

 

Yup. If your talking Jeff's car, yes, I run the stock Brembos with Hawk HP Plus up front, I think he runs something more aggressive.

Keep in mind, for Autocross, you don't need a ton of brakes. I rarely used the brakes fully, unless I was already late for a corner. If you look at some of the Street Prepared guys, a lot of them run the smallest brakes they can, as it saves weight, and massive amounts of cooling aren't needed in autocross.