Idle surge after Stillen supercharger install

NissanTracker

Hi Forum,

I'm having issues with idle after my S.C. Install. At startup in closed loop, idle is fine. After warmup and transitioning into open loop, the idle is terrible. Will go up to 1K RPM's and bounce around up to 1,500. I do see the fuel trims increasing.

The tuning shop went through a compression and leak down prior and numbers were good. 210 on average across the cylinders and leak down was less than 10%.

A boost and vaccum test was done and all is sound. MAFs were cleaned out and I also pulled the throttle bodies out and cleaned them (battery disconnected and unplugged the TB's before taking them out)

If I cap the PCV, the idle surge disappears, which would lead to a leak somewhere... But boost and vac test came back fine. I changed the PCV after that test and still nothing. I may have an exhaust leak between the drivers side manifold and high flow cat. Can an exhaust leak cause this idle surge with forced induction? I had a leak there before and I never had idle issues. I figure the supercharger has changed the dynamics and wanted to ask.

Some info:
07 350z Nismo @53k miles
Standard Stillen kit (no upgraded pulley, no fuel return, walbro 255 fuel pump with the regulator tapped with provided drill bit)
Kinetix HFC and a Tanabe Y pipe to factory OE Nismo exhaust
Probably irrelevant, but I also added a Mishimoto oil catch can(closed)
Has a custom tune (dyno'ed at 350wHP), idle set to 800rpms
1+ step colder plugs (370z spark plugs- standard gap)
Replaced Stillen provided BOV with a authentic HKS
Z1 oil pan spacer
34 row oil cooler

Never had any issues before, solid as a rock


Much appreciated,

-NT