I had a pretty bad coolant leak on a new to me 2008 JK. The jeep has 180k miles on it, so I assumed the lower intake manifold gasket needed to be replaced. I did the job myself, and everything went well I thought. Engine started right up after, no codes etc. Still had a coolant leak after, but it was less than before. Next morning cold start, started experiencing misfires on cylinder 6 only for the first 10 to 20 seconds then smoothed out. I assumed, high miles bad fuel injectors. So I replaced all of them with cheap ones from amazon. They ended up making the engine run worse, and threw new codes out. I then bought the correct bosch ones, and had the same misfire cylinder 6.

What I'm wondering is if the lower intake manifold install wasn't done correctly and could cause the misfire? Or could there be air in the fuel rail or elsewhere? I do occasionally get the small leak in fuel light (gas cap one). Just trying to get this through emissions and I'm chasing my tale with parts and time.

Installed the following on it so far

Lower Intake manifold gasket
EGR Valve
Catalytic converters and pipe
O/2 Sensors
Fuel Injectors
Evap Canister
Gas Cap
All new brakes, and speed sensors (had a code)
Spark Plugs, wires, and Coil