With Evo 8 ECU use Evo 8 ROM.
Tephra ROM preferably

 

Having problems sourcing intercooler piping here in the U.S. for my evo 4, shipping overseas would kill me

 

With some modifications, you can fit any Evo 8/9 piping kit on your 4.
I managed to fit an Injen piping kit along with an evo8 AMS intercooler on an Evo 5

 

ive got an evo 9 lower pipe and intercooler fitted to my evo 6 just needed to mod a couple brackets and the new cold side piping was rerouted fills in much better in the evo 6 bumper openings instead of having the gap on the sides the evo 8/9 intercooler is larger by about an inch over the evo 5/6 intercooler

 

LG7Two4

The later Evo piping will not fit early Evo...
Any suggestion you can modify: you can modify anything..but you are not any closer than starting virtually from scratch.

I recommend you assemble and have it fabricated locally. It will cost similarly to purchasing new,
perhaps check if Tomei can supply you a set- because Tomei in USA distributes their products and can supply those not -normally uS parts if you patiently wait for the "next shipment" of goods. I know from first hand experience.

HKS use to be able to do that, but they stopped really supporting USA directly.

Another source is Canada...now that they get tons of JDM cars...somebody can supply pipes.
And I would still dare to ask HKS distributor...and I would also ask RRE- RoadRace engineering...they may have a set laying around?

 

Installed the spec r kit and without a retune the climb of boost is alot smooter, spools up to 24psi about 500-1000rpm sooner in higher gears.