Oldsmobile/Buick Repair: 97 Skylark check engne and ETS light on at same time, egr valve, vacuum leak

Question
My new to me '97 Skylark custom  2.4 with 68,000 miles
check engine and ETS light just came on this week at the same time is that normal? the mechanic says it is a bad EGR code and 4th cyl miss fire code
codes p0404 and p0304.both lights were on and off from time to time earlier this week but now both on at start up by the way.the car seems to run smooth at least for now.
Is it normal for the traction control light and check engine to come on at the same time?
..Does anyone have any tips to deal with the EGR short of replacement. Thank you for you time.  

Answer
The EGR valve is intended to be removed and cleaned.
A dirty EGR valve, closed on some carbon, will act like, and in reality actually be, a vacuum leak.
It could cause the codes, and cause it to run rough, or have low power and bad fuel economy.

Van