Re: power pack replacing
The original power pack on your motor incorporates both QuikStart and S.L.O.W.
QuikStart advances the timing when the engine is cold and allows for the easy starting that you have come to expect. The black and white sender wire off the port cylinder head temperature sensor is the signal wire that tells the power pack to advance the timing.
S.L.O.W is also activated by the same wire when the sensor signals that you have an overheated condition,
When the engine overheats, the powerpack reduces the engine RPM to 2500 and will not let you override it until you turn the engine off AND the engine cools back to < 162º.
There are blocking diodes in the wiring harness that prevent other warning signals from reaching the S.L.O.W. sytem.
What Sierra part number are you installing? Does it incorporate both S.L.O.W and QuikStart? You will want both.