Blows Main Fuse at 1/4 Throttle???

I'd say you have a dead short somewhere and when the car moves and shakes it finds its path to ground. 30 amps is a hell of a lot of current to be pulling. Check the top of your fuse box to see if some stray piece of metal (or screw) had not fallen on it. It happened to me and drove me nuts till I pulled it down and found it.