I too would like to thank the people who posted their EGR valve information on this site. I had the SAME EXACT problems with the VTM-4/Check Engine lights coming on, the P1491 code along with some of the signs discussed on these threads. ('01 MDX, 71K).
I called Bob Howard Acura in Edmond Oklahoma and was told that it would cost me $80 to have the car "hooked up" to the computer (like fair compensation for pushing in a plug and letting a computer tell you what's wrong is $80...give me a break!). They then told me that they've never heard of EGR valve problems with the MDX. I told them about this forum and how seemingly hundreds, if not more, are having this same problem. When he said he doesn't buy into chat room information on the internet I let him have my Ace in the hole where MSN's model research details how the EGR valve and the Evaporative Emissions Bypass Solenoid are problematic on the MDX.
I called my local mechanic (Ranchwood Autoworks in Yukon) and they told me they would check the car with the computer, if all it needed was the EGR valve and gasket there would be no charge for the diagnostics, but if something more showed then they would charge me....fair enough.
Customer service at Bob Howard Acura in Edmond Oklahoma is non-existent. Their main objective is to rip you off!