thanks Dabsy and Vader. based on your suggestions, i've done some research and plan to start with replacing the stock cross-pipe panel filter and air intake box. seems to be an important factor and looks relatively inexpensive and easy enough to do. i found some decent performance parts online for less than $600 for both (aFe Power MagnumFORCE CAI and MagnumFLOW panel filter).
i also did some reading on ecu remapping. looks like a good option to boost hp and torque and maybe even get a few extra mpg. i'm interested in doing that but i saw warnings on the use of low-cost chips and inexperienced companies. the key seems to be finding a reputable company that can do a complete diagnostics of the engine and provide an honest recommendation of how or even IF to proceed based on the findings. unfortunately, i live in dayton ohio...not exactly a hub for bmw performance activity. any suggestions on a good place in the dayton/columbus/cincinnati area? Or are there any good companies where i could maybe buy the chip, have it programmed/shipped, then installed locally?
exhaust and under pulleys will be next to review Lord Vader!