Ok, you screwed yourself and will stay there until you rework your exhaust. Throwing away an easy 40+ ft. lbs. of torque is on you. Totally ridiculous to ask for help and throw it away.
If you actually feel like your 416 has a lack of torque, revisit the reply above. Also add in, headers to small. Next size up is what you need for more torque.
More torque, more mileage.
Sell the entire system and get the next size up header and work the exhaust system like I said.