Heat soak is a concern with a blower. WMI does help in that regard.
Honestly the best bang for the buck IMO is a lower gear ratio
Swap in a 3.64, 3.73 or if you are really crazy a 3.91 from an X3.
The torque multiplication of a 3.73 over a stock 3.07 is 21% more.
I can attest to the seat of the pants increase. You in to the power band so much quicker. 60 mph has the engine revving at 3000rpm.
http://www.bokchoys.com/differential/GearRatios.htm
For me cams are only worth it on an all out race build.