Working on a 13 FRS had a hydro locked motor, replaced with a forged internal engine has king bearings, Manley rods and Pistons 12.5.1 compression. And perrin lightweight crank pulley. When starting first thing it starts the high revs then sputters and dies. Restart starts right up stays running but misfires and coughs and sputters the whole time it does the cold start process. After that runs perfect drives fine no codes other than p1603 and p1604. I'm not sure what else to check. Ive changed the di ecm on the side of the motor no change, tried new MAF new upstream O2 sensor, different throttle body, smoked the intake system found no leaks. Fresh 93 fuel put in. It's driving me crazy because it runs so good after the cold start. Also if it's warm or hot like you stopped at a store and went in for an hr and restarted the car starts up no problem and runs fine. Has to sit for at least 4hrs or so till the coolant temp gets back down to 80 degrees or less for it to act up.
