I own a 96 jap spec fd3s, I have removed the cat and replaced the rear box and cat with a custom built 3" system.
Since replacing the exhaust and the temp here in England dropping, I seem to be experiencing boost cut when in 4th or 5th and accelerating hard from 4k+ as the boost seems to creep out of control.
Also general boost pattern is 0.9bar spike then dropping off to 0.6 on second turbo here it seems to hold
I believe that this is due to undersized wastegates unable to cope with high flow/high load conditions but would appreciate any advice.
One of my next mods is an uprated air box, but I fear that this will only add to the problem.

 

Ahh yep..it's the wastegate...time to enlarge it

 

have you done any fuel mods yet? If not you might want to consider doing so before you moddify the intake. Running lean would be a very bad thing i.e. so long motor. Also to help control the boost spike if you make your exhaust a little more restrictive it will help increase back pressure, and should reduce the boost spiking problem. or you could just look into increasing your wastegate opening. Have you converted to Non-sequentials yet?

 

Yeah, since you added those items without upgrading the ECU you will definitely hit some cut. Get an APEXi Power FC or an upgraded ECU of some kind and it will keep the boost under better control. You may want to look into enlarging the wastegate down the road though since it involves a lot of down-time. The ECU upgrade would help the most at this point in your mods...