Novice

I've recently been given a 1993 Silverado heavy-duty pick-up truck that, it's had it's previous engine swapped out for a 502. I'll be making a few threads with questions because most things I find on the web aren't relevant to what I'm seeing under the hood. I've ordered a Haynes repair manual (it hasn't arrived yet). The wiring has been 'tampered' with, it's got and additional computer installed that controls the super. It's been diagnosed by a mechanic, nothing shows up. From what I know he hasn't checked anything out on the additional computer that regulates/controls the supercharger.
It didn't always start when I was given it, sometimes needed additional fuel sprayed into the supercharger. It had an injection-issue. Fuel supply seems to be ample. I'm not sure about the compression/injection of fuel into the combustion chambers.
When put into to gear it moves but won't accelerate beyond 20-30 km/ 10-15mph.