New ignition problem

[mazspeed]

Ok, here is problem number 9086230 with my car. I had everything ready to go for the show this last weekend. I was taking the car to the gas station in town that has 100 oct. I'm coming up highway 9 in 3rd gear, not really pushing hard, when all of a sudden the tach and engine go to 500rpm and jumps up and down real fast between 0 and 500 or so. I was able to park the car on the side street. I went to start it several times and it would start, but not go above 500 rpms and the tach would go nuts. I let it cool down, started it back up again, and I was able to drive it about 2 miles before it did it again, then I opened the hood and let it cool down, then got in and babyed the car home. I have not started it since. The car sists in the garage, and a stong raw fuel smell is coming out of the car as it sits, and it has some sort of ignition issues. What do you guys think this could be? MSD box? J&S box? The float levels in the carb are a little above half way which is good, what gives?