I didn't realize there were different EGR valves, so I got curious and did a bit of reading for you. Yes, for vacuum controlled EGR valves (the type used in our B230 engines) there are commonly different valves used with automatic and manual transmissions in all makes. The difference in design appears it may just be the diameter of internal porting.

It's done for the sake of minimizing emissions during normal driving conditions. The valves are opened and closed using engine vacuum, which of course varies with engine load. Most references I saw make note that compared to a manual transmission, automatics place a slightly different load on the engine at idle and during acceleraton and deceleration. The EGR valves are designed to respond differently to open and close more similarly under the slightly different vacuum conditions.

So that now begs the question of why don't turbos and NA engines also use different EGRs? The engines do have very different vacuum profiles over the rpm range, with turbos having a vacuum pump. It may well be as Grey245 suggests having a lot to do with your foot staying on the gas in addition to engine loading.

The 6842769 EGRs for manual trans appear to be more readily available from sources. Based on my reading, although it may affect gas mileage a little bit, the difference in performance between using one type of EGR valve over the other should be minimal. If anything, I would expect using a possibly slightly less responsive EGR designed for a manual might make for slightly improved performance in an automatic at the expense of a little gas mileage. However, because the later ECUs monitor EGR operation through a temp sensor and are able to electrically control when vacuum is getting to the EGR then any effect may be extrememly subtle.

I found an old thread here on the brickboard that you may find interesting Hacking the EGR System. The KittyG replies are especially well done with great pics and info.

For more general information on EGR principles of operation, here's a mildy interesting technical article I found on the Hella website Exhaust Gas Recirculation
--
Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now