j.packsb

so ive got a turbod d16y8 and ive already had the car tuned. Im running a straight t3 50 trim with a .42 intake and .48 exhaust. i was tuned on 12 pounds with a 5 lb wastegate spring and a turboxs MBC. a month ago, it was holding 12 lbs perfect with no spiking or falling off. now all of a sudden the boost pressure started falling off? its not falling off enough to be a boost leak at all but slowly falls off from 12lbs to about 9-10lbs at 6k rpm. i thought it was the boost controller maybe so i took it off and ran just a heavier wastegate spring and im still lost. its holding 12 in 2nd gear falling off to 11.5 by redline but in third it spikes to 14 and then at 6k falls to 12 lbs??? im lost and have tried everything! I dont understand how it can be falling off or spiking when using just the wastegate spring. i also tried moving my pressure source from the compressor housing to my brake booster line.... still no change.??? help plzzzz

racemycivic

I know you said you dont think its a boost leak, but have you boost leak tested all your charge pipes because i have seen this happen when there is a boost leak or perhaps a tear in a vaccum line

j.packsb

i would think if there was a boost leak then it wouldnt be holding a steady amount of boost it would just completely fall off?? and a tear in the vacuum line would cause a vacuum leak correct?