right ive just completed my 2.1 ZVH conversion, car seemed to tick over and run sweet at first, now it seemed to have developed some sort of problem and i just cant get to the bottom of it.

It starts both with the chip in and with the chip out but wont idle, it will revv but seems to feel like its missing, im not sure if it may be down to fuel starving so i change the fuel pump relay but the pump is priming fine.

Can any1 help me out, what else could cause it not to idle and seem like its missing.

Thanks in advance
Matt