I had my car mapped two days ago (widetrack blob sti), the drive back after the map was fine, however I completed a 200 mile motorway journey today, and the boost is fluctuating wildly.

At first I thought it was a random fluctuation, but there does seem to be a pattern.

The car will sit at 1 bar for a few seconds, boost to 1.2 bar, go back down to 1 bar, then boost to 1.4 bar, down to 1, up to 1.6, back down to 1 etc.

The clutch isnt slipping as there is no corresponding sudden increase in revs, stopped at a service and I did not see any split pipes, no cel light, nothing.

Have any members encountered a similar issue? I have installed a new dump valve gasket, and Im not sure if the dump valve is opening when this happens (still on oem recirc).

Current mods are :

billet 321t
prodrive sports cat
2.5" exhaust,
800 cc injectors
induction kit with k&N filter
HRC 255 fuel pump.

Any help would be greatfully appreciated

Car has been a bit more difficult to start lately, but this maybe a seperate issue?

 

Have you tried cleaning the boost solenoid? I had the same problem, cleaned it out and all's fine now. Also if you search "boost" it brings up all sorts that might help you.