To all you guys wanting to know about accelerating in 5th .... Use your gearbox!!!!!!!!!!!!!!!!!!!!!!!!! That's what its there for!!!!!!!!!!!!!!!! If you need or want to accelerate from 60 in 5th quickly eg to overtake safely, swap back to 2nd or 3rd, boost it, get the move done, and shift back up again. If it's a limit change from 60 to 70 or 80 then light throttle with the speed of the traffic in 5th is plenty adequate.
for me... when my car was pinging I changed my driving style so not to lug the motor at low rpms. So, if crusing at 60Km I'll be in either 3rd or 4th. 60-80Km I'll be in fourth gear. 80+, and I'll switch to 5th. I usually rev 4th gear to 90km and then go to 5th. Cheers