Sounds to me like you've got a possible arcing problem. Re-check your plug wire connections at the plugs & coil pack. Make sure the wires are not cut/cracked. There should have been a couple of ground wires that needed to get re-connected when you installed your new coil pack. Make sure you got them secured properly.
EGR valve
I need to write a How To on this...
To test the EGR valve go the the closest auto parts store & buy about 2 feet of hose small enough to slip onto the little EGR vac nipple.
When you get home, leave the car idle & unplug the vac hose from the EGR valve - plug in the 2' hose.
Pull a little vacuum on the hose (yes, you suck boy). Your car should start to idle rough or even stall. If the car does not at least run rough, you've got a bad valve.
You should be able to get the car running rough & keep it there by holding a vacuum. If you have to continually apply more & more vacuum, then the valve has a leak & is in the process of totally failing.
