Back in 80 My brother and I bought our 73 Charger Rallye 400 Magnum. The guy before us has flipped the Air Cleaner lid. We went to flip it back and the Sticker that said 400 on the lid was permanently charred from one of many previous Thermoquad fires. LOL
Needless to say we kept it flipped until we got a new air cleaner.

Can't say if it helped with power or made it louder but it looked better than the cooked top side of the lid.