The only valve I can think of in the exhaust is an EGR but that connects to the inlet
Often it may be possible to temporarily block the end of the exhaust with holding a cloth over it and eventually if there is no leak the engine will (should) stall due to the back pressure. Otherwise you should get at least a better indication of where any leak may be
Often it may be possible to temporarily block the end of the exhaust with holding a cloth over it and eventually if there is no leak the engine will (should) stall due to the back pressure. Otherwise you should get at least a better indication of where any leak may be