Hello We have two 1970 Road Runners six pack car, Engines is the same, one has TTI headers ($835.00)and the other has stock manifolds,Both have 3" with 40s flowmaster all the way , one with chrome tips,one with turn downs,Both have 410 gears, one auto trans other 4 speed. The Stock manifolds car sound better and has more power then the header car! both cars have a H pipe also. Is it the stock manifolds ?All but one of the last 10 cars have stock exhaust and 3" pipes. MY Is headers is for drag racing ,manifolds stock street cars 450-550 HP , no engine heat under the hood. no gasket troubles.no floor board heat, again