I used a fully modded Shelby Cobra 427 with racing tires and about 800+ bhp, just to win at Deep Forest. The tactic was to keep to the racing line, and avoid being overtaken by the Toyota 7 and the Chapparal 2J.
If anyone is going to take my advice, make sure the Toyota and the 2J start 4th or lower. A fully modded Cobra can leap into the lead coming out of the first corner.
Can you post your car settings? I'm trying now with the Cobra and I can't find the right suspension and LSD balance especially for the first few corners.