Pulls good then loses boost. Wastegate maybe?

[Froyd79]

I have been searching for a bit but havent come up with much. I have a gt30r and it will pull and spool to 16 then drop to 11 or 10 and feel like its just blowing hot air. Every gear every time. I have put in 2 different mbcs and the same result even on different settings. BOV goes as normal. Honestly the last time I checked itn had a leak at the Intake mani gasket and I replaced it and it ran good perfect boost everytime. Since then added the gt30 and a fmic. Those tbolt clamps are tight and I even added a new TB gasket. Went to napa and bought 30 feet of vac hoses in 3 different sizes and replaced all lines. I can keep hitting the gas and letting off and hitting it again and bosst will build and drop and spool up and haul ass but give it full throttle and it acts like I have mentioned. 0 counts of knock 2 degrees of timing in boost trims are al a tad on the lean side. I dont know much about this wastegate but I have had boost leaks and it doesnt feel like a leak per say. It is a 17lb and i messed with it a tad before installing the turbo. Is there a way to check that its fully closed or anything?

 

[Froyd79]

Not sure if it helps but I am at 20vac at an idle. Was 15 when my intake man. was leaking but its at 20 now. So like I say she spools quick and hard for like a second hits 16 and drops to 10 and feels like I am running al motor but I can hear air rushing ( and I mean rushing) through my exhaust. This turbo also has a 4 inch inlet any ideas on how to do a thorough boost leak test w/ this puppy.