I know the XT660 is a cool bike. But to be honest if you want to do wheelies and hard acceleration. There are better options. Better sell it and get a KTM 690 Supermoto and be happy. Problably the costs and especially the time will be much higher to invest into tuning the XT than getting another bike. The KTM 690 is lighter and has plenty of power, plus you will be driving a road legal bike. I know you have invested lot of money and time into the bike. But sometimes its time for a change . Plus with 40000km on the clock its still possible to get a decent amount of money when you sell it. With more than 50000km it will get harder to sell the bike.