I still have that X-Treme lid around here someplace, gathering dust now for quite a few years. From the testing I did, the engine ran flawlessly with the stock lid, or no lid at all. The stock lid has a pretty tall "rise" in it compared to the flat X-Treme lid. My q-jet and set-up simply didn't like the lid, others have reported that they work fine, but I've never had anyone report making any more power on the dyno, or running faster at the track after installing one......Cliff