hello, I have a 90 gmc 3500 4x4 454 my problems are these : engine seems to idle to high warm or cold. at idle truck will acccelerate to over 30 mph on level ground,seems faster in reverse. have replaced air throttle control, new throttle body gasket. next problem: way to much heat in engine compartment,can cook on hood and fenders after even a short drive. has new cat and muffler dual exhaust. any ideas?