Hello, I may need a new idea. I have an "87"Vn750 with carb problems. I still have the original exaust pipes on it, minus the baffells and crossover. Also have the K&N air filters. The carbs have 147.5 main jetts, with two spacers on the needles. I still have backfire problems and a skipping\starving at mid to upper rpm range. I ride any where from 4000ft to 6000ft. Would any body have another idea for me?