Someone tell me why im overboosting

[The Morris]

This is my story
i was running a bleed valve with no problems. Changed to a grainger valve and at the same time put on a 2.5" downpipe. The car was over boosting. I was getting 8 psi until 4000rpm then it rose to 17psi. We decided the fault was the downpipe and you could see marks where the wastegate flaps were catching it. So i got a replacement and it looked a bit different. This time the same was happening but i was getting 15/16psi which was fine. Any way i fitted a cone filter and im getting 17/18psi. I just took the gringer valve off and no change.
So is it the downpipe, the wastgate or the actuator. Ive had the actuator tested and it seems ok. i dont want to spend another £200+ on anew downpipe and have the same problem. Its just strange how i get 8 psi until 4000rpm and then by 4500rpm im hitting 17psi.

Someone help.

[The Morris]

PS its a rev2 and ive disconnected the vsv and replaced the pipes between the actuator and wastegate

[Bry]

I've got the same prob with my rev 4,everythings fine till about 5k then the boost starts to creep up.I haven't got any special down pipe or hybrid turbo which are known causes of boost creep,mine only seems to do it when the temp drops down(air temp)it's ok when it's not too chilly

[raptor95GTS]

my understanding was that if the VSV was disabled and the pipes blocked you would get the base boost which is 7psi on the rev1/2 and 10psi on the rev3+.

As to why you have this problem dunno

[The Morris]

my understanding was that if the VSV was disabled and the pipes blocked you would get the base boost which is 7psi on the rev1/2 and 10psi on the rev3+.

As to why you have this problem dunno

I do untill 4000rpm

[PW@Woodsport]

the actuator isnt opening the wastegate far enough for some reason by the sound of it...are you running the stock turbo or uprated? even when theres no grainger and the turbo is plumbed directly to the actuator and the outlet from the actuator is blocked off it still overboosts?

[The Morris]

Standard turbo. I didnt block the pipe from the actuator instead i cut the wires in the vsv plug as i couldnt unplug it.