It will idle up to about 2000 rpm, runs fine, starts coming down, running good, drop to 700/800 rpm, starts spuddering, does not kill. And I am hearing a loud hiss, like there is a vacume leak, somewhere between the engine and the fire wall.

Moved to cars and trucks

Thank you Mr. Chuck. I could not figure out how to put it in the right category.

Vacuum leak, plugs, plug wires. Bad injector, fuel filter, bad fuel pump. Heck even a weak battery can cause problems with newer vehicles. Probably far cheaper to pay someone to put it on a scope and run a diagnostic test.

Possibilities:

. PCV Valve Hose Emission Separator, which goes from the PCV Valve to the throttle body. Over time, engine oil that is evaporating though the PCV Valve deteriorates the rubber "L" going into the base of the throttle body.

. DPFE Sensor hose leak.

. Upper Intake Manifold (UIM) leak--replace O-rings.

. Lower Intake Manifold (LIM) leak--replace O-rings.

. Idle Air Control Valve (IACV) leak.