Ill keep this as short as I can. New to the forum as well. I made some adjustments on my 2003 zx9r carbs. put in new needles and springs, drilled out mixture screw plugs and have at 1 3/4 turns out I beleive. Bike ran like a boss after I did this. Still a small hesitation in quarter throttle but made a huge difference. The factory pro jet kit came with bike, I think all they did was put the jets in and obviously didnt do anything else. Ran great for a week, then one day it started up and as I started down the road something was very wrong. After thinking of the simple things to try first, I ended up putting sea foam in the house that runs to my kleen air system. For whatever reason, it ran fine after that. Didnt seem quite as powerful but may have just been in my head. I put about 80 miles on it in 4 days or so. Then driving home from work, it happened again. Would not start back up very easily, like it was on 2 cylinders again. I put sea foam in that same hose again and let it sit for 5 minutes, then it started right up. I drove it back to my garage, hammered on it the whole way, no problems. Cylinders 1 and 2 run, but 3 and 4 are having issues. Anyone have a suggestion? I am not a mechanic, but have done some work on a couple of my bikes, I am not an idiot. Youtube and these forums have been great with information. I just can not find anything similar to this for info on what might be wrong. Please help! I am about to just say screw it and take it to a local shop.