Hello, I have a 2000 Pontiac Grand Am GT 3.4L V6 with aprox. 150000 miles, when I got this car(in early 2005) it had 114000 and ran SUPERB, but I have noticed a decrease in performance, it's running good but not excelling like it did. 3 months ago I did the car's maintenance and it really helped out but I'm starting to feel again that drag and slumpy engine feeling and sometimes it just wont run like it did, can you help me out regaining lost HP without making big modifications?? there's got to be a way to improve performance without changing intakes and exhaust systems...