Re: Upgrades for 3.9mpfi
Jim Mock Motorsport is down in Melb area, and do the cam/head/ exhaust thing for I6's.
There's debate over the validity of their power claims, but most people who have used have been pretty happy with the results. Mind you, they aren't cheap from what I've heard.
Try a search on "mock", "JMM*" or similar - should turn up a few threads.
Unless you enclose a pod properly, and give it a decent air supply, your not really getting anywhere - you might breath easier, but it will be nasty hot air. A panel filter is the best way imo - although you might be able to find a better airbox / intake to suit the car - so investigate that *before* you buy an expensive filter !