My 04 stx-12f is very hard to start. It has now started only running up to 5500 rpm when it should hit 7k... top speed is only 38 mph... it also builds alot of pressure in the gas tank while trying to start and when running. not sure if this is normal, but if you loosen the gas cap after trying to start, it has enough pressure to actually shoot off when it clears the threads.. any info would be appreciated...