Well we got everything bolted back together today and fired her up and it started smoking kinda, but we figured it was just some oil or something that'd spilled on the headers during the install. Turned it off, went in to eat, came back out and turned it on and the smoking had kinda subsided, so we backed it out and then it started popping out of the drivers side exhaust. Anytime we put it into gear it'd start popping and running pretty hard, especially on the drivers side, then we threw a p0300 "Multiple/Random misfire" code. Anytime it's in park it runs fine, put it into gear and it starts popping again...we checked all the plugs/wires/anything ignition related and it all was fine so we're thinking it might be leaking coolant into a cylinder or 3. Anyone want to confirm my fears? It was spitting out a decent amount of smoke from the exhaust after we drove it for a quick little drive out of the cul de sac and back, and anytime we'd give it gas or a load it'd pop like no tomorrow. We also pulled some plugs and one of the plugs looked a little darker colored than the others, although it wasn't easy to say if it was fouling or not. The plugs we pulled were on #1 cylinder and then the front and rear cylinders on the drivers side. The one that looked sorta iffy was the one on the front of the drivers side bank of cylinders, closest to the thermostat. I'll get some pictures uploaded of our gasket/RTV layout just to show you guys. Probably a coolant leak though?