Ok so let's start off, I'm new here and just wanna figure this problem out. So let's start with this, I rebuilt my 2001 4.0l grand cherokee motor about 3000 miles ago, everything internal in the block is brand new, bored it out 30 over because I lost piston number 1. I had the head resurfaced and used the old one, little did I know it was cracked but I will get to that. Got it running and was running fine for about 2000 miles, finally figured out the head was cracked so bad it had to be replaced. I got a recast of the imfomis 0331 head, it has a thicker deck, put new springs, valves, it already had new rods and rockets. So theres a little back story, finally got it all back together started it up and it was running fine for about 45 minutes while my mechanic buddy was there, of course he leaves and it starts misfiring. I changed a map sensor, put a new ignition coil on it, replaced the injector that said it was misfiring on, put new spark plugs on, have sprayed brake clean to find any vaccum leak and nothing. I'm stumped and can not for the life of me figure this out. Im about to throw my hands up and take it to a shop. Please help me jeep community I would really appreciate it.