To anyone with plenum spacer, Did you're 350Z's idle at the same RPM's level it did before this upgrade. When I did the pop charger and the grounding wire's the idle got smoother and down in my car and it was filling very good. The reason I asked is because my Z, when I did this upgrade my idle went up and ones in a while the rpm's goes up pass 1000 rpm and down, like small spikes in accelaration. The idle in my car still smooth is just that this behavior puzzle's me because maybe I still have a small vacuum leak in my car. Can you guys help me understand what could be happening.

 

I never noticed any differences after installing either the spacer or the isothermal gasket kit. Most of the time, fluctations in RPM are caused by a leak.

 

I'm suspecting a small leak too, but I don't know where to start. I was tinking about re-tighten the bolts on the plenum a little bit. What you guys think?