my crown victoria is showing p0108 and I changed the mass air flow sensor and gas cap do u think it could be the pcv valve or the egr valve
P0108 is the DTC for MAP circuit high. This means you have either a faulty MAP sensor, usually part of the engine ECU in later vehicles, or you have low manifold vacuum. This can be caused by incorrect cam shaft timing (new belt lately?), valves adjusted incorrectly, or a simple air leak on the engine some where.
pretty sure MAP sensor is part of EGR assembly, can't be purchased separately. test for 5v power with key off. at idle, the signal wire (to ecu) should be in the 1v range. if it is more than 5v at idle, it is bad. could be other things causing the code too, but this is a start. check youtube for vids on subject. good luck.