How do I find out if I have a vaccum leak.I'm beggining to suspect this cause after my intake swap ....my Z28 has been running slower.I was looking closely today at the intake and noticed that there was black sh_it around the intake bolts and the valve covers are sealed good and arent leaking , do I have a vaccum leak????

 

Rough idles are usually dead giveaways for vac. leaks. Get some carb cleaner and spray it around where you think there might be a leak. If the idle changes, you gotta leak.

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89 iroc-z 305 tbi
k&n filtercharger, open element air filter. nuffin' else

 

How would I check for a vacuum leak on a TPI engine, cause I have a very rough idle and thats what some people told me it might be.

 

put a vaccum gauge on it, stock vaccum should be around 19 - 22 in/hg on an engine in fairly good condition, if it is way low and you have a stock cam, there is definitly a leak