Throttle Position Sensor: TBI V8 - 82-83 Corvette & Trans AmT. P. S for the CROSS FIRE INJECTED 305 V8 auto or manual. This helps regulate the flow of fuel and in idle of the vehicle. Sometimes also known as the TPI Switch rather then Sensor. Common complaints when faulty is iratic idle.. goes up and down.. hard to keep at an even speed pace.. may also \"run on\". (Reminder that Electricals are non returnable once sealed bag is open.. its so nobody gets previously played with parts.)