1991 Formula mx 462 won't idle. I can get it to idle right but when you hit the gas the RPM's go way up and the only way to get it to down is to back the idle way down then readjust it. After above 3-3,500 the sled runs great. The carbs have been cleaned and set right, Fuel pump and lines replaced, pulse line replaced. The compression is 160 in both cylinders. The fuel tank was drained and cleaned and the filters replaced. Does the engine have a bad seal? How can you test it without a leak down tester?