What is the best combination for Cam and manifold with 87 tbi 350, for use on and offroad, also whats the best upgrade to do to a tbi sys?  

yeah I can't tell you about the cam and intake other than go fully rollered (roller cam, lifters, and rockers) I have a hypertech chip and airaid throtle body spacer on my 95 chevy with every thing else stock and i think they are the best things you can do for the money.