the normal ones are:

sloppy suspension due to old rubber suspension bushes -(fit PU ones)

electrical gremlins due to naf fusebox and engine multiplug connection - (new fusebox and join 2 looms togeher without connections)

oil consumption - a cossie will gobble a litre of oil every 600 miles (FROM NEW!) the oil never dropped at all inbetween services on teh evo.

breather system - the cossie one can just about handle 280 brake - but on older more tired cars with more blow by this needs upgrading also - the evo breather system is fine to around a good 400+ bhp.

an evo will run 350 brake out od the box with a pipe fuel pump and chip.
the cossie needs new chip, pipe, pump, injectors, sensors, breather etc