Solved! Not a bad coil, but a bad connector to the coil. It's a 2003 so it's not surprising that the inner plastics of the connector were starting to come apart. My temporary fix until I salvage another connector was to pull the positive and negative wires from the connector and directly connect the...

I've tried both a new coil and swapping spark plugs from the bad with the good. It still misfired the same. I am running the NKG plugs as well

Additionally while i can get the car started amid all the misfiring, if i turn the air conditioner on or put the car into gear it will often stall out.

I'm experiencing the exact same symptoms as you, on my 2003 S40 1.9t 84k miles. Did you ever figure out the fix?

Hello! I’m the new owner of a 2003 Volvo S40 1.9T with 84k miles from Georgia (United States). While accelerating from 40 up to 65 mph, I simultaneously had both Cylinder 1 and 4 misfire while accelerating but resumed normal operation once at a constant speed. The car drove fine for 2 hours with a s...