Nellsw88

Hey everyone, New to the forum here and don't really want to introduce myself with tech questions. But long story short, I recently traded my built yj wrangler for a 95 z28 with 67k on her. This is the first newer v8 I'm dealing with, I always played with first gen small blocks so this is pretty new stuff to get used to. The car has sat for a while and had the heads and valves done about 1000 miles before I got her, have the receipt from previous owner and was done by a pretty well known shop in the area not in a back yard. Also has new water pump and plugs, but they neglected the opti and the car was in need of a tune up.
I installed new fpr, filter, and pump, fixed the start up issue. This past weekend I decided to bite the bullet and put on a msd cap and rotor, not a whole unit, it ran relatively fine before I changed them, even though the original cap and rotor was corroded, now it starts relatively easy but has a revving idle like a vacuum leak and hesitation under heavy throttle. I have a funny feeling I forgot the seal between the cap and isolator, I'm assuming that possibly is my problem. The vacuum lines are fine and hooked to correct ports.
It has to be something stupid I did because it was good before, or I somehow got a faulty unit.
Thanks for any help you can give me