Thanks again, pwogaman. Will check them out for sure.

Meanwhile, I discovered that the muffler shop did not have the header pipe snugged tightly to the manifold after they replaced the manifold gasket. Snugged it up and, so far, do not detect any odor. But I think the flap thing is something that I ought to check on anyway--sounds like it could become a problem if it's not working properly.

Joe B.