Wow you done alot to fix the alero misfiring.
First find the miss by touching the exhaust at the cylinder to see which cylinder is misfiring, while it warms up. It will be cooler than the other cylinders.
Second check compresion readings.
Third make sure you dont have vacuum leaks.
Im sorry cant figure out what BTW means but I think you changed those items. Id recheck your work, its running but incorectly. It could be effecting all your cylinders, like timming off a degree and thus compression gonna be way low.
The egr might effect idle but it opens above 2000 RPM's. Its the diafram thing about 2.5 inches wide mounted up on the intake near the throttle valve I never seen your model but I doubt if it has a tube from the exhaust pipe to it which makes it easier to find.