94 C280 Check Engine Light issues

[DavidF.C280]

Hello Everyone,

First Time Poster, but I hope to be more active I just found this board :-)

My Problem is with the Check Engine Light which Keeps coming on, so you know its a 94 C280 with 98K. This has been a Problem on and off for the past three months, here is some background.

CE light Came on, and my then mechanic replaced both O2 sensors, in less than a week it was back on again. He suggested the EGR valve, which had already been replaced under the service Bulletin, but would give no guarantees as to wether this would solve the issue, Or in other words he was asking $700 (O2 Sensor and EGR valve R&R) for a "Maybe".

So it was off to the Dealer, they were getting the same codes O2 sensor and EGR, as well as a cylinder 1 misfire, but they replaced the Air Flow Control Valve/Sensor (Will double check but I am 99% sure that was what they did) and put on new plugs and leads. cost $1000. Its Ten days later and the light is on again. Its Booked to go into the dealer on Thursday 10/12. Just so you know I am in the DFW area

To sum up I have two questions.

1. Any thoughts on what could be the problem the EGR valve is the only thing that has not been replaced, but as I said it has been replaced before.
2. I have yet to discuss this with the Dealer, but in your opinon do I have any recourse with them if they charge me full whack to do what they diagnose this time. IMHO I am paying dealer rates ($100+ per hour) I should get the service to match.

All Opinions/Flames welcomed.

David