99em1boost

Hey guys, so the other week i was at the race track, ran the car hard, shook real bad, lost spedometer and odometer, tach was intermittent. When the car has power then it works, as car starts to lose power tach will die. The battery is somewhat new and tests fine. So I replaced the alternator, thought my problem was fixed. Plenty of power, i get two miles down the road and the tach drops and i see my lights dimming, then while driving the car just dies.
Now, I know it could be a bad alternator even though it is new, but what else could it be? please help, really struggling on this one.

99em1boost

Update... Alternator is good, battery is good. I am now just blowing alternator fuses and the speedometer and odometer worked for 4 miles today and then went away. I assume it needs a new vss and there is a possibility that wires may be rubbing underneath causing this fuse to blow. shower i choose a fuse with more amps? (note: all grounds look to be good)