sounds like your timing chain, if it was your tapets or valves it would be consistant regardless of idle or anything. as crazy1 said, these tension up with oil pressure, ride it hard after like a week and give it a few days, if it still taps after this time then take it back to the shop and get them to take a look at it FREE OF CHARGE.
p.s: it is a little highly priced for some labour work of which could have been avoided if they knew what they were doing but i do think that not so many people of this forum need be so negative and constantly remind binky77 of the price he paid. as long as he is happy with how it works and didnt mind paying that kind of coin, who are you to remind him of the fact that the price tag was a little steep...? if binky77 didnt mind the price, so be it. glad to hear you got yourself a mean machine binky, hope its just slack in the timing chain and nothing to dramatic. i would also suggest calling them now and telling them off the issue, see what their reaction is and base your decision to resolve the problem on that. if they say, bring it down and we will sort it out now for you, cool, if they say we will need to take it off your hands for a few days, then thats something completly different. good luck champ
Cheers, Tony.