I have an automatic 2006 Legacy GT wagon with the turbo. It has about 185,000 miles on it. I just had a complete rebuild of the engine by Outfront Motorsports in Buena Park. They installed forged WRX pistons, ARP rod bolts and WRX engine mounts as upgrades for helping the engine last. They did a great job on the rebuild and are very helpful if I have any issues. My only concern is that I have piston slap in cylinders 2 and 4 but it doesn't effect the engine other than noise.
Under hard acceleration, like merging onto the 91, my check engine light flashes and the transmission holds the gear up to redline. When I check the codes using my TORQUE app on my phone, I get P0304, and P0303, Powertrain cylinder misfire detected. Outfront can't seem to replicate it when they have the car. Also, sometimes the car is hard to start after I clear the code.
What could be the cause and how to I remedy this issue?
PS, The turbo has been rebuilt within the last two years; I use Rotella oil and change it at 4k miles.