2006 XC70 is misfiring under load. It seems okay under 3000rpm and behaves normally, no engine check light. Just drove 6 hours straight under 3000 rpm and no problem. Mechanic ran a diagnostic and it showed a code for the MAF and cam position sensor. Tried a different MAF with no difference. Above 3000 rpm it starts misfiring. Could the cam position sensor be the issue or is there a chance the coil packs could be playing up without throwing a code? Any advice would be appreciated before I start spending unwarranted dollars.