Got Shell 93 Octane and now barely idles 1973 Dart 340

Disconnected the vacuum line to the brake booster and plugged the manifold fitting. I got my highest vacuum reading setting the A/F mixture screws at 15.5-16" of vacuum. Plugged the vacuum advance and advanced the timing until the the RPMs raised and lock down the distributor and set the idle speed to 850 rpms.

Then reconnected the brake booster and started the engine and it's running like crap with vacuum gauge bouncing from 12-15" of vacuum and a higher idle. I cover the choke with my hand and rpms go up but still running like crap. Plus the hissing is back and I can hear it directly coming from the brake booster check valve via my ear and the noise via touch.

Looks like the brake booster/check valve is bad causing another vacuum leak. The hissing started at the same time of this issue started and the brake pedal has been soft and low since I got the car.