My 94 ls has been stalling recently. It still runs strong but idles very slightly rough at times and then stalls if it sits for more than a few seconds. It has an underdrive pulley, adjustable cam gears, intake, and exaust. All mods have been on the car for over 3yrs and dyno tuned. I have cleaned the air filter and replaced the fuel filter. It ran great for a couple days after each but then resumed its old habits(I'm thinking it did that because I unhooked the batery each time). The most likely things that I can think of are the fuel pump, EGR valve, and vacume leak. If you know where the EGR valve is please fill me in. What do you think is wrong?