For the record, I have a 1990 740 GLE 16-valve DOHC with about 126K miles on it, with a manual transmission (4+ OD). What can be done to it to make it go faster? Is there anything that can be done cheap with a fair return in performance?

So far, I have put slotted rotors from IPD on the front, and semi-metallic brake pads all around. When I next replace the rear brake pads, I will replace the rotors with slotted rotors. Is there any more that can be done for the brakes? I've heard that putting 960 calipers on it will help. I have also put Bilsteins and overload springs in the back. I know most of the handling upgrades that can be done (lowering springs, bilsteins, anti sway bars, etc), but I have yet to find much in the way of actual performance enhancements, as they are mostly for turbo engines.

I have been thinking about getting a K&N filter, if only for the gas mileage increase. However, there is a turbo filter and a non-turbo filter. What is the difference? My engine has higher compression than the non-turbo, so would I benefit from a turbo filter? (My compression is 10:1, whereas the non-turbo is about 9:1) Same with the IPD performance exhaust. What's the difference between the turbo exhaust and the non-turbo exhaust?

Is it possible to replace the camshafts and/or timing gears? I was looking at Unorthodox Racing in relation to the pulley and saw the gears, but it kept trying to load when I wanted to plug my model in to see if they had any for it. I'm on super fast Cable, so something was wrong with the site.

Any replies are appreciated, thanks!
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Manual tran 16v Wagon... Booyah!