A mate has a V6 VU ute and asked me for advice. He changed belt tensioner, and since then it runs badly, stuttering between 1500 and 2000 RPM. Then goes okay at high revs. Oddly it happens to be dual fuel, and does same thing petrol or LPG. So we checked spark plugs and vacuum hoses. Changed spark plug leads, and I had a spare DFI coil, and spare MAF sensor so tried swapping them, no improvement. Also cleaned the contacts on DFI module. It does not have any error codes. The crank angle sensor had been changed about 18 months earlier. So what else is left? Throttle position sensor? Exhaust sensors? The PCM?