I need to know what the purpose of Toyota part #90925-05068 is for. It's mounted atop the out port or hot side for return to radiator and has 2 vaccumn hoses that hook to the top. Is it necessary for the engine to run properly or could a plug be put in that hole, and the vaccum hose is plugged off?
=========== TVV (thermal vacuum valve) used to regulate vacuum at the EGR modulator. AFAIK, keeps the EGR off until the engine warms, so disabling it would interfere with proper operation of emissions control, would guess primarily higher NOX from higher combustion chamber temperatures. You've got to believe it was put there for a reason. With computer controls, once you change one component, you're likely to impair the operation of the engine rather than improve it.
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