I've got an 2005 withthe Buschur Stage III, this consists of the following:
FMIC
Intercooler pipes
Mas Air pipe
TBE
Fuel Pump
Air filter
HKS 264 cams
1G BOV
Buschur Flash
Buschur MBC/EVC EZII

In addition I added the Dejon kit to the 1G BOV to make it hold at higher boost pressures.

The problem I having is I can't seem to tune out a 3 psi pressure drop. If I start out at 25psi it will taper to 22. If I start at 22psi it tapers to 19, 20 to 17. Just to make it confusing if I start at 16, it will hold 16 all the way out.

Boost peaks at 3200 and stays constant for 1000 RPM and them tapers 3 psi by 7000. I first thought it might be the BOV so I made a block off plate for it, no difference.

I then pressure tested the entire system, no leaks.

I had an extra wastegate actuator, so I swapped that. SAME.

With me suspecting the MBC I ordered an HKS EVC-EZII and installed it. Guess what, I still have the taper. The EVC does not have any gain adjustments just boost settings, so it might be a gain issue on the EVC?

I'm out of ideas. My goal is/was to hold 20 psi from 3200 to 7000. The turbo can hold 22 at 7000, so I'm not running out of turbo. Anyone else have any ideas?

 

How high of a psi did you pressure test the system ? Did you plug the uper IC hose that goes to the T-body ?

 

Pressure tested it to 30 psi. Ran it both with and without the throttle body side capped. Car is making good power ->320 hp on a dynapack at 19psi at 7000.

 

dang , after 17-18 psi my system was leaking through the trubo sleave's bearing's and making a "dripping'' sound in the oil pan ..... Iam sure you checked out Buschur thread and been reading about his "probs'' with the boost dropping off , some talk about the pressure diff in front/rear the wg flapper and the pressure ''could'' be cracking it open . I would love to hear a true fix for this .

Matt

 

boost taper is normal for a modded evo on the stock turbo. Mine is set to 22psi and it will drop to 18.5-19 psi by redline. Even David Buschur has taper on his RS. Not much we can do about it.

 

Sounds like a leak. Even if you can't find it, is your whole system t-bolt clamped? What about the IC pipe off the turbo -- that's a really common place for a leak. Your car is just silent when you pressurize the system to 30 psi?

I don't have any issues like that with my Buschur set-up. It peaks at about 19-20 psi the way I set my Blitz ebc and it falls a pound at most from peak. For the most part it's just rock solid throughout the whole RPM range.

Also, have you logged timing or AFR? Could it be pulling timing in the upper RPMs?