HELP!!! Car not boosting

[gsx187]

Hey all just got my 98 gsx 2 months ago and it was driving fine some issues here and there but nothing major. I went to my mechanic to fix up some exhaust leaks on the turbo manifold and down pipe. Got the car yesterday driving it on the high way everything was fine holding 10psi of boost. Went to the store turned off my car and then on the way home wanted to floor it again and noticed my boost gauge not going into boost, slam on the gas and it just goes to 10 or 5 in vacuum but not in boost and I'm at 5000rpms??? I get home and I'm reving it up at idle to 4000rpms and hear a load BOOM from my exhaust and my gauge does not even go to zero when i press the gas but to like 5 vacuum.

*also I have a garrett t3/t4 turbo 60 A/R M24 and I get full boost (10 psi) at maybe 3500-4000rpms in second gear is this normal?? or should it be sooner.
-Vibrant big FMIC and hard piping
-MBC (set at 10 psi)
-External Tail waste gate with dump tube
-turbo manifold
-3 inch apexi exhaust
-walbro 255 fuel pump (stock injectors no fuel pressure regulator)
-blitz BOV recirculated
-custom clutch with kevlar disc pressure plate good to 450hp
-new fuel filter
-NGK wires and plugs
-autometer boost guage
-KN air filter

 

[Dsmj89]

Sounds like a deffinitive boost leak, check your couplers and make sure none popped off, and check all your clamps and make sure they are tight as well.
Also make sure your vac lines are connected and that your wastegate isn't staying stuck open.
If the above fails, check for fouled spark plugs and/or cables.
Let me know if this helped out.

 

[gsx187]

Hey thanks for the fast reply...Yeah I made sure everything was tight and found out that 3 of the 4 screws holding the manifold were loose and the manifold was pretty much holding on with one screw tighten that up checked my vac lines, and went for a drive and its back up boosting..... problem solved...Also another question whats the normal rpms range I should get full boost by with this set up I have..Is full boost(10psi) by 4000rpms normal or slow??? I still have to get my car tunned ...and what injector size should I buy was thinking 550cc or bigger my goal is 350-400whp ....

Thanks