This may be old news to some but with soring gas prices it should be worth repeating.I've done this on 4 cars already with every one reporting large gains in milage and power. The problem is that between the heater door ,related brackets and mechinism a large restriction to air flow is caused.Solution:Remove It all!This is most easly done by removing the heater door Assembly from the air box and carfuly spliting it in half (pushing on release tabs)Remove heater door brass thermostat and spring then cut away all plastic bracketing then reassemble finish by covering over hot air inlet.How car will peform in cold weather remains to be seen.In the mean time you should be able to remove the word "Slug" from your vocabulary