hi there have you tried changing the variator to a malossi one this make a huge difference to the performance. it should come with 6 gram and 9 gram roller weights. i oppted for 3 of each it increases your acceleration and increases your top end by 6mph. if you put the 6 gram rollers in you will get great acceleration but the same top end, and its the opposite for the 9 gram rollers . a malossi variator will cost around £55 from ebay if you cant get one for a xor 50 try a cpi hussar they are the same engines. good luck .