Been a long time since I posted here about my full size blazer, she's had a lot of work done recently and I've gotten to the point where I'm stumped.

Short story: brand new crate long block installed 2 years ago. Ran like a champ until a wire across the exhaust manifold melted and shorted. Sat for two years before I found the problem. had 1/4 tank of bad gas in it. goto it running again after fixing the burnt wire but i think the bad gas caused some issues. It started as pinging, but even after draining the tank and filling it with fresh gas it steadily got worse to the point it was difficult to start. I was trying to limp it back home when it overheated and blew the oil cooler line out of the connector on the engine. I stopped it before I lost all the oil.

So far I've replaced the oil cooler line connector, changed the fuel filter, changed the MAP sensor, changed the EGR valve and solenoid, and changed the fuel pressure regulator. Each new component improved the condition slightly. Now it runs pretty smooth, but it is backfiring out the exhaust AND into the intake, constantly but with no rhythm. the exhaust backfires are loud as hell too. Fuel pressure to the TBI is testing at 12psi. Anyone got any ideas what could be causing so much backfiring?