I recently replaced the intake manifold gaskets on my 2002 lq4 and I can still hear a vacuum leak and still have rough cold starts. I had a lean code causing random misfire code and the intake gasket fixed that bit I can't find the other leak. I tried spraying brake clean and had no luck

 

do a smoke test on it

 

I chased a vacuum leak for a week recently, took the intake off multiple times, never found anything at all... finally decided to swap the intake it's self, I found 2 wrecked bottom injector o-rings (the spare intake had flex-fuel injectors so I had to swap them)... replaced the o-rings, codes went away, truck runs great and all the fuel trims are correct now... I tried brake cleaner and even ether, neither would show up in the idle speed...