For the 551 code, check the IMRC solenoid to make sure it is not unplugged. Check the solenoid coil for proper resistance (50-100) ohms. If it's plugged in and the solenoid coil tests good, then you either have a wiring harness or PCM fault. The IMRC solenoid is on the firewall side of the engine next to the EVR solenoid,
The 327 is very likely the EGRP (Dpfe) sensor. There are a few other causes so additional diagnostics should be performed to prevent unnecessary parts replacement. Refer to the PC/ED for exact procedures.
Steve
