I'm a little stumped here. I'll try to type this out as coherently as I can.
Friend just bought this and I've done a ton of work to it. CV axles, axle seals, cat converter, plug wires, intake gaskets, resealed valve covers. After doing all that I discovered the lower crank pulley bolt had been left loose by the PO and the pin was sheared in the t-belt sprocket and the keyway was demolished. Found a replacement at pull and save for 6 bucks or so from a 2000 3.0L engine. So, the t-belt came off to do this with careful marking and replacing. The marks line up perfectly. Unless this has some oddball procedure like my Isuzu it should be fine.
Throttle response is laggy and it feels like it should have more power but the biggest clue, I think, is the popping from the exhaust. It's not constant or even rhythmic. The fact that it only does it when the engine starts warming up tells me that it's fuel going down the exhaust and is being ignited by the hot cat. I know, not good for the new cat. Anyone ever have this problem before that can point me to what might be going on? Bad fuel injector maybe? Some other sensor causing it to dump fuel for some reason? It only idles a little rough. It was doing this before, IIRC. I do remember the sluggish throttle and it seemed to me to be bad ignition components. Oh, also I can see with my timing light a misfire on #1 and the frequency of the flashes varies from one cylinder to another. Some are fast flashes, some are half a fast.