Here's the deal. Just sold my 74GT750 because it was a basket case. Found a 75gt750 in great shape. Original paint in like new cond, eng and cases look great etc.. Eng seems to run well, but it bogs down at anything over 1/4 throttle under a load. Does not seem to be pulling hard at all. Most likely needs a tune-up. But my last GT had bad crank seals, and I dont want to go through all that again. What should I check for???