^This ... I'm sure- like me your used to WOT in 5th to pass cars on the freeway ...You shouldn't be doing that in 5th... It is your drivetrain about to explode.
Do the revs go up at all and then come back? If so, that's the first symptom of a dying clutch...Straight line and does anyone else have a problem in 5th gear if I get on it in 5th it takes a second then the boost hits is it just lag or the stock piping expanding