Check if breathing heavy, good way is if the oil filter cap lifts up or falls off after a good kick in

You want to see it from cold start (not started before you get there)

Check for smoke on start up, on boast and on lift off

Alittle puff of black smoke on gear change is ok but make sure it's not excessive

Flat spots on boast or it popping and banging while on boast

Oil leaks

Tapping, if it is it's not the tappets it's the cam it's self due to bad design.

And make sure everything feels tight and on road test

And if you know about rust areas that's ok but alot of people forget to check around the rear springs on the chassis legs

Good luck mate