One ton, I'm pretty sure I know what happened - you had one injector loosen in the head, not enough to cause major compression leak, but enough to cause that misfire. After you cracked the lines open and then tightened them down chances are you also tightened the injector back in the head somewhat, hence the lack of scarey noise now. BTDT, first time (cylinder #4) I never felt it but saw it as tiny air bubbles when the base of the offending injector accidentally got soaked in WD40, second time tho (cylinder #5) it happened to me down at Toledo Speedway and since I was more concerned with keeping the race car running I fixed it when I got at home, again after visualizing the issue by spraying each injector's base with WD40. And today while bleeding the lines after turning up the pump I noticed that my #6 injector seems a bit loose in the head, and it was, so I tightened it down before I tighten the line nut onto it, no more compression leaks. So at this point I'd suggest that you spray something (considering you got a turbo there WD40 is probably a bad idea, so use soapy water instead) at the bases of the middle 2 injectors on passenger side, and watch for tiny air bubbles, if you see any you'll need to tighten that injector down good, which may or may not require remove of the return cap and lines from it.
Any idea where on the motor the noise is coming from?
