Lexus engine problems?

I have an issue with a 1996 Lexus ES 300. Yesterday I changed the oil and filter. Then I hooked up my scanner to retrive the codes for the MIL (P0402 - EGR Excessive Flow) I thought perhaps the EGR is clogged up with carbon. The car has 172K miles. I manually opened and closed the valve spraying intake cleaner in it until the fluid came out clean, then reinstalled it. The car ran fine at first then it started to miss and carry on, MIL came back on. I realized I forgot to hook up a wired connection off of the EGR valve. So today I hooked it up, scanned the codes and cleared them. Five codes in all (P0401 insufficent EGR flow, I forget the other numbers but the descripts are misfire cyl 1, misfire cyl 3, misfire cyl 5, and multiple misfires. I drove the car around for a few hours and it is still missing, but only at idle and not all the time. No MILs, the idle drops and revs lightly and makes the car feel like it is trying to lurch forward. I did more searching and found a dead solenoid that feeds the vacuum to the EGR valve. I replaced the dead solenoid at the tune of $110 and the car is still doing the same. Only effected at idle, and not all the time, probably in 5 minutes segments. ideas? PLEASE?