Pilot Unloader Valve 140 PSI
Bostitch Air Compressor Parts

Price: $136.16
Found under the following brands:
Chicago Pneumatic, US General, Belaire, Kobalt, NAPA, IMC-ATLAS COPCO
1/2" FPT top inlet and 1/2" MPT bottom outlet. Has 1/8" FPT for throttle control line and drain cock valve on side. 110 on 140 off