Boost issues

**msr1** · 01-09-2009 12:54 AM

A friends car is having some issues after installing a forge wastegate, FMIC and new vacum lines + MBC only spikes at 8psi in first gear until 3k rpms and then drops to 5psi, in all other gears the car only holds 5psi in some high gears it also drops a bit. If you turn just a bit the MBC gets a limp mode and reads overboost.
???

**B5A4Kevin** · 01-09-2009 06:25 AM

how much vacuum does it pull at idle. low slow boost with low vacuum at idle is a good indication of a boost leak. are there any faults? you could also be hitting soft limp mode. i had a faulty maf that kept me in soft limp with a dtc for lean multiplicative.

**msr1** · 01-09-2009 07:41 AM

it reads 20 of vacum. the only fault that reads on vag com is overboost. if you have a faulty maf, will it read on the vag com?

**doublezero30** · 02-13-2009 04:11 PM

I have this same issue. I just did my intake mani gasket and valve cocver gasket. Checked the hoses which i had to take off and all areconnected. Car is revo stg2 with all supporting mods. Spikes and holds at 5psi in all gears. Any hoses i should check that i mighthave bumped? Thanks!

**J Ozzie** · 02-13-2009 04:23 PM

when your driving and let off the gas the vac should hit 25.. does it do that?

**Seerlah** · 02-13-2009 04:27 PM

Originally Posted by msr1

A friends car is having some issues after installing a forge wastegate, FMIC and new vacum lines + MBC only spikes at 8psi in first gear until 3k rpms and then drops to 5psi, in all other gears the car only holds 5psi in some high gears it also drops a bit. If you turn just a bit the MBC gets a limp mode and reads overboost.
???

Did you get a Forge wastegate (for a reason I do not know unless the wastegate was damaged. but if you meant diverter valve, then that is understandable) for the stock turbo, fmic, mbc, and think you can just up the boost?