A race cam has the cam profile engineered for power @ high revs ... imagine a car with no power till 5000 rpm then it wanting to rev like nutter till 9000 rpm upwards!
errrm, not quite.
the "normal" driving becomes a pain cause the engine is rough as nails until you reach a high rev. you can expect idling to be >2000rpm, which makes the car especially painful in town.
you can run any motor up to 9000rpm, you just need to change the return springs on the valves. the reason that engines have a rev limiter is because the the valve generally wont shut fast enough, causing an overlap, and then hell kinda breaks loose. by putting a stronger return spring in place, the valve snaps shut that much faster. thereby allowing you a higher rpm without blowing the engine away.
forget drilling airboxes and the like and changing the exhaust.
generally, get yourself a new standard exhaust, get the air filter changed, and renew the injectors. far simpler and much better results than faffing around in the engine bay for weeks.
if that doesn't work. buy a 16v.
