Weird boost/studder problem Please Read..

[DJ23GSX]

Ok to start off these are my mods:
Ported 16g, 560's, SAFC,Ported 2g exhaust man and o2 housing, 3" turbo-back exhaust, 3" intake pipe with K&N, ACT2600 SS line, MKIV i/c, 2.5" upper and lower i/c pipes, Magnecor's, bpr7's, Fluidyne radiator, Walbro 255lph pump Weapon R AFPR

Heres my problem.... With the Apexi silencer in my muffler i am able to run 21psi without any problems at all. I am getting 0-1 counts of knock and 18-20* timing and my o2v are between .84-.86 (90 GSX) all the way to redline in 3rd gear. After removing the silencer and running the same boost i get this bad studder near redline. My knock spiked up to 40 timing got yanked and my o2's when crazy. I tried to richen things back up quite a bit on the safc but it only got slightly better at best. I turned down the boost to 18psi and was able to lean it back out almost to where it was when i was running the 21psi with the silencer in. I can definalty feel a difference between the 21psi with the silencer and the 18psi without the silencer but i cannot seem to figure out what would be causing this problem. I did do an intake test and i do have a decent size leak. I think it is the intake manifold gasket because it sounds like the hissing is coming from under the motor near the firewall. Even with this leak why can I run more boost with the silencer?

Any help would be appreciated.
Thanks

 

[Burnett03]

Ok to start off these are my mods:
Ported 16g, 560's, SAFC,Ported 2g exhaust man and o2 housing, 3" turbo-back exhaust, 3" intake pipe with K&N, ACT2600 SS line, MKIV i/c, 2.5" upper and lower i/c pipes, Magnecor's, bpr7's, Fluidyne radiator, Walbro 255lph pump Weapon R AFPR

Heres my problem.... With the Apexi silencer in my muffler i am able to run 21psi without any problems at all. I am getting 0-1 counts of knock and 18-20* timing and my o2v are between .84-.86 (90 GSX) all the way to redline in 3rd gear. After removing the silencer and running the same boost i get this bad studder near redline. My knock spiked up to 40 timing got yanked and my o2's when crazy. I tried to richen things back up quite a bit on the safc but it only got slightly better at best. I turned down the boost to 18psi and was able to lean it back out almost to where it was when i was running the 21psi with the silencer in. I can definalty feel a difference between the 21psi with the silencer and the 18psi without the silencer but i cannot seem to figure out what would be causing this problem. I did do an intake test and i do have a decent size leak. I think it is the intake manifold gasket because it sounds like the hissing is coming from under the motor near the firewall. Even with this leak why can I run more boost with the silencer?

Any help would be appreciated.
Thanks

fix the boost leak, end of story

 

[DJ23GSX]

Yeah I know I need to fix the leak but I want to know why it doesn't have the same affect when the silencer is in??