You mad some critical errors. Testing with dyno headers was a giant waste of time and money. You didn’t learn a damned thing doing that. Same with the air cleaner.

Run the engine on the dyno as close to the way it will run in the car. So basically your dyno numbers mean nothing.

Also, stop using ET to calculate your HP from the time slip. ET is hook. MPH is Horsepower.

You have no idea other than guesses what your engine actually makes for horsepower on a dyno. I’ve seen dyno headers beat chassis headers by 40 plus HP. That was header to header. There is now way you are only losing 30 HP going to manifolds unless the dyno headers are garbage.