Ok i had and exhaust leak when i first installed ottp header. When i was done and the leak seems to be gone. Im going to drive it more when i have the chance to make sure. But i used The Fel Pro Composite Gasket and a GM donut gasket. Now the problem is that theres a casting edge on the head that doesnt allow the flange to fully seat on the head. I to clearance the flange on the header.