Ive recently noticed on my del sol, if im full throttle in 3rd gear, as im approaching the red line, my gearstick starts to shake a little back and forth, its only when the revs get high though, what could it be??

 

Well, assuming the engine's working right, I'd guess a motor mount.

 

Its probably nothing to worry about. The shifter is attached to the transmission, which is attached to the engine, which has things called pistons and other internals that move, causing your shifter to move.