Emergency!!! ECU help please!!

ok i have a 92 integra with a b20b block b16a head… it did have a generic chipped p28 that ran fine… i traded this guy for his p72 which he said would work, when i put it in the car would barely start, would only run if you gave it gas and lots of white smoke from the exhaust :bawl: … it had cels and he thinks its probly knocks or something… so he comes out and gives me the p28 back and now the p28 does the same thing… they are both obd1 and i dont know why when i put my old one that use to work in now it doesnt work… i reset the ecus every time i put new stuff in…
please help me out fellas!:crook: