I just bought an 89 camaro rs 2.8, it has running issues that I've been trying to narrow down.

It used to start pretty well, but didn't have any power and horrible throttle response when you'd blip it. Fixed a bunch of vacuum leaks, replaced the TPS for the old one was reading wrong, replaced cap, rotor, wires, plugs still look good so I kept those, found that injector 6 was unplugged, reconnected that, and replaced fuel filter. It started running slightly better but still would backfire out of the intake or the exhaust.

So after some reading I thought timing could be the issue, so I disconnect the single wire connecter set timing to 10°, pull the ECM fuse, reconnect the wire, put the fuse back.... and now it runs even worse. Lots of back firing, smells horrible, throttle just kills it now. What did I do wrong here?? Ive checked wire placement, I haven't replaced coils or anything yet but I dont think those would be the issue..