85 monte 4.3 erratic idle

so I swapped my old 4.3 for one out of a 86 chevy blazer. the motor ran great in the blazer but after getting everything hooked up I get erratic idling and poor response from the car. throttle body is new as well any ideas where to start?

Look for vacuum leaks and an egr valve not seating closed.

Thank bud I'll give that a try I noticed the sensor for the egr broke any clue where I can get a new sensor

Try napa or a dealer.