Hey all, 04 Blazer with 85k miles. Issue has been on and off for a while. Weird issue for sure to bare with me. Starts up fine and runs like a champ. Sometimes though while going up a hill it will seem to misfire and the check engine light with flash in bad cases usually on the highway going up a hill, but doesn't happen often and will go away once the road is level. There are NO check engine codes. Along with this, after I shut it off and it's been sitting for an hour it will crank over a lot longer before it starts and wil hesitate, but will start and run fine.

I have changed the fuel pump, filter, plugs, wires, cap and rotor, and alternator. And I just replaced the upper and lower intake gaskets along with new oil and a coolant flush. I've done all this as general maintenance, not just trying to fix this problem. My next guess is the coil but I thought I'd get some opinions first.