I know the EGR takes unburnt gases from the exhaust and recirculates them back through the intake. On a 2001 4.3L how does it put it back into each cylinder? Reason I ask is if it goes to each cylinder individually and some of the passages are clogged (say to cylinder 1 and 4), would that cause problems that are hard to diagnose?
Also I know the EGR engages when you are decelerating but is it only when you let off the pedal fully or whenever you are slowing down?

 

The EGR outlet tube runs into the very open plenum on the newer SCFI motors. The location allows these gasses to be pulled into all cylinders somewhat evenly. The only way that EGR gasses would not make it into a cylinder is if the intake runner to that cylinder was plugged up completely and that would definitely not be difficult to diagnose...

The EGR valve can open while cruising, decelerating, basically any off idle fully warmed up state other than WOT can have the EGR valve open.