ok...recently i had to change the wires and coils for the EGR valve...that fixed the problem..than 2 days later the CEL comes on again..i get the codes read...O2 sensors both front and back..i change those..fine....NOW the cel is on again!!

what could be wrong? the car drives perfectly fine!(tho it does make so sort of viberation noise rarely from time to time in the engine compartment) ive taken it to mechanics and have the codes read with high tech computers..NOTHING.....wtf could it be???

timing off? bad ECU? what!?!?

oh and BTW...ive also given it a full tune up..wires, plugs..all that good stuff.