1993 Chevy Silverado Hei computer timing

Hi i recently rebuilt a motor and put it in my 93 chevy pickup, i am having problems i believe with timing. I was told a computer chip would help solve my problem, tono avail. I can start the truck it will idle fine, about 5 minutes (after warm up) it idles down almost dies, then it starts to surge. I am just about certain it is a timing problem. But i am unable to find information on how correctly time a computer controlled hei ignition system on this year vehicle.
Oh, also it is backfiring thru the tbi, i took it for a drive and at first gear it was fine, but shifting into second above 30 repeatedly backfires thru thecarburetor and will not even stay running. Thats about the extent of my problem. any help would be appreciated. thank you