If you want maximum performance out of the impact gun, install a high flow coupling to the compressor & HF fittings to the line/tool.

Husky High Flow Aluminum Female Quick Coupler and Plug Set-036-0138H - The Home Depot

This is done to provide MAXIMUM volume (CFM) to the tool @ rated pressure (90psi).

I've seen mechanics up the pressure regulator to remove tough fasteners, dumb move. Housing failures can remove fingers, or worse, getting your hair parted by an impact hammer!.

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'03 X5 4.4 Sport, last of the M62s (8-03 build date)
I believe in deadication to craftmanship in a world of mediocrity!