Boost Cut - 1998 WRX STI - version 4
 

i'm new here and have only had my Impreza for about a month now.

its a Version 4 Wrx Sti

Modifications are:

3" turbo back exhaust including sports/highflow Cat.
K&N cone filter
ARP head studs.
A'pexi power FC with commander unit.

i was supposedly setup by Andy Forrest (i have no proof of this)

my local specialist is Clive Atthowe engine tuning.

he put 3 boost settings on there.

1 bar = 288 bhp / 230 lbs ft
1.1 bar 288 bhp / 234 lbs ft
1.2 bar 294 bhp / 249 lb ft

can post graphs / AFR graphs if this helps.

The car seems to hit boost cut in 4th and 5th when starting from low revs..

so if i rev out 2nd and 3rd into 4th its fine.

build up boost from 2000Rpm in 4th or 5th and it hits boost cut at 3500rpm - 4000 rpm.

strangely it seems to happen less so when running 1.2 bar so i run it on this setting mainly.

Clive mentioned that the apexi can cut boost when it goes 0.25% over what it is set at. and i have noticed it will spike to 1.3 bar when its foot to the floor in 2nd. he did also mention that it seems the previous owner wound the wastegate arm in slightly and it seems stiff, he mentioned that being a 1998 these can often become a bit soft etc as you would expect over time but this seems to be a bit stronger..

should i be looking for new parts like a 3 port boost solenoid or an upgraded wastegate actuator from forge ?

is this something to fix in the tuning side of things..

any help would be much appreciated.