I've heard that IV engines suffer from 'crank walk' (which isn't good BTW).
Spend a bit more and get a V or better yet a VI. No major engine problems that I've heard and they are tuneable. AYC can be an issue if its not been properly maintained.
Ditto above. Save some extra pennys and go for a V for the better engine, or a VI for better engine & brakes & looks IMO & other little tweaks (check out lancerregister for more info)