Just got a bf zr6t mk 2 its go usual mods exhaust cooler and seimens injectors Have done 200kms in it so far and its developed a tapping noise Only on idle and not at higher rpm , performes well and runs smooth ,noise increases when A/c compressor kicks in , the fella I got it off reckons that's it is injectors Noise and it is imminent ( sometimes does it and goes away) I'm thinking it might be timing chain , any input woud be appreciated