I have a 1990 chevy s10 2.5, 5 speed. Recently bought this, installed new plugs, wires, cap, still has a little engine miss, when i rev and hold it misses some. Could there possibly be some sort of a vac leak, or what are some things to look for? Thanks

First for sure make sure that there are no vacuum leaks. Get a vacuum guage on there and see whats happening. If all this checks out, do a compression test, check and make sure pressures are good and fairly equal.

where do i check vaccum at, whats it suppose to read...

Normally their is a vacuum port on the intake with neoprene cap you can remove for a test gage.
I usually use a can of carburetor cleaner and spray along the edges of the intake manifold and other items and hoses. If the spray hits a leak the engine will smooth out. Watch where you spray avoid plug wires.

What I use for vacuum leaks is a spray oil. The reason is it is not as flammable as carb cleaner. JUST DO NOT USE WD-40 IT IS VERY FLAMMABLE. Carb cleaner being sprayed close to intake carb or throttle body will cause idle change many times just from the residue floating around.

i had the same problem with my 95 s-10 2.2L. there is a vacuum line that runs across the top of the engine in the very back along the firewall that was original factory. i never would of noticed the vac. line was rotten on the underside and allowing air in. a vacuum gauge would of been a faster option of finding the problem.