Reaper is right, TOP ENGINE CLEANER, available at your local GM dealer. When i first got my K-5 it ran like...well it didnt really run. I dumped TEC down the carb(follow the directions). It ran so good after that treatment, cleaned it right out. You can also clean the injectors with TEC when you mix it in with the fuel, but its not recommended cause it melts some bosch injectors /forums/images/graemlins/eek.gif