Had a Jasper manufactured engine installed after a major problem as a result of coolant leak. Researched installers in south jersey, used a location with the best reviews. After two weeks got the car back, very sloppy work, wiring harnesses not routed properly, heat shield not properly secured, plug wire 3 on exhaust manifold.egr valve code. Plus more. Problem is car never threw a code, now I'm seeing Po 303 misfire on 3 ,po137, low voltage bank 1 sensor 2,car breaks up on hard acceleration, really pissing me off. Had transmission services, filter and new fluid, changed plug 3, and plug 3 wire,new egr valve. Not sure what to do next.Car is in great shape,love the car hate the problems that I see as a result of a poor install. Any suggestions?

After you replaced the #3 wire and plug, did you clear the codes?

P0137 is the O2 sensor. Looks like downstream of the cat. Make sure wires are connected and or not touching hot exahust.

I'm not sure how the 2000 series O2 sensor is connected, I'm kinda wondering if maybe they forgot to connect it just based on how the 97'* are.

Yes, replaced both plug and wire. Wondering if it could be a fuel injector?

missfires can be fuel related too, you could swap it to a different cyl see if it follows. look for damaged o rings while you have it out

re-read your problem, did you try swapping coils to see if that changed the cyl? check over the wiring to see if the wires to the injectors or icm are good.

I swapped coils and the misfire followed, replaced bad coil and down stream O2 sensor. Took the car out for test drive,jumped on it a bit 5k rpms, no misfire lots of power.

Boo ya!!! Glad you got her fixed!