In purchasing a 98 Monster 900 last fall, I inherited a problem. I'm no mechanic so my terms may not be too clear, but it seems to be rather "congested," especially when you reach higher rpms. It backfires too much also. The origianl owner replaced the exhaust with D & D pipes and added a K & N kit . He said the dealer told him they had trouble getting it to run right after installing the pipes and re-jetting. He said it fouled plugs a lot after that. Here is my real question; a respected local Japanese and Aprilia mechanic who looked at the bike for the previous owner told me that he called several Ducati shops when he was trying to fix it and they told him when you change pipes you need to change carbs also to make it run right. This just doesn't sound right to me - anyone ever heard of that? I'm thinking of trying to find a set of factory pipes to put back on it - it's too loud to suit me anyway. Since it's not my main ride I'm looking for the cheapest fix. Any ideas or opinions?