worst case scenario, you warped the brand new heads. at this point, at a minimum, you will need to replace the head gaskets. since the 90deg after torque was not done, and it "overheated", the gaskets are useless. since you are gonna have the heads off anyway, get a good straight edge and feeler gauges to check heads for warpage. make sure to get new head bolts again if this is the case. now, there are a few things to check, and pray that luck is on your side. coil packs replaced, but what about spark plugs and wires when heads were redone? pull the plugs now and see how they look. if coolant got into the cylinders it could have fouled the plugs. if they look bad, replace them. it is far cheaper and easier to do this than re-doing heads and so on. check for vacuum leaks too. you could just have some injector o-rings pinched somewhere(an example, but vacuum leak could be anywhere.) I am sorry if i am deliverig bad news, but i won't sugar coat it. hope you are lucky. let us know how it's going/