had 4x4 cossie tuned today but its over fuelling, the tuner tryed to adjust the co level but as soon as it dropped it went straight back up.he reckons it could be a mismatched chip and injecters. its got green 355 injectors and the chip got nec 1990 on it.if i get a new stage 1 chip can i use the 355 or will i need standard injecters.thanks