easy fix on the svt you can do yourself for about 15 bucks. ive found on alot of svt's its the engine grounds.
go to a stereo store and pick up 10' of 6 gauge fine strand power wire,4 solder on ends with a 3/8 inch hole in them (these are used under the points on the block shown), 2 with a 3/16" hole (mount 1 to each fender under an existing ground point), and 2 with a 1/2" hole (mount under nut on battery negative clamp).
for grounds its not necessary to heatshrink or tape the ends, other than to make them look better. at each mounting point make sure it it clean and has metal to metal contact. hardest part is measuring and soldering. which really isnt hard