78gbodywagon

Hey people I'm new to this forum, I've been reading all these posts & tips on all kinds of posts on almost everything to a ls swap. But haven't came across this yet. So I got a 78 Malibu wagon with a 2004 5.3/4l60e,O2,ls1 intake sensors with standalone harness (dbc)(blue&green) done by a friend. I just recently started the engine & got misfire on #1,7,2,8. Give gas & loose power. I pretty much checked all injectors,coils,plugs,spark plugs. Did the light pulse test on injectors & those injectors plugs (1,7,2,8) light goes on with ignition but then once engine starts, pulse stops. So pink wires tie in the crank sensor, how do other injectors pulse fine & other ones don't. Need some help, trying to figure this out myself before the (friend) gets time to diagnose this. Anyone ran across this & is it something I can do without taking all the harness back out? Also checked out codes on obd & no major codes pop up. Computer or tuning issue?