Well, actually I needed to pass a very slow driver on Hwy 154 ( a mountain road) at the only available place to pass and then ran up on another tourist driving the "scary road" and had to break it down to not rear end them. After seeing the smoke, I intentionally did it again to try to recreate the event and did. However, today I inspected the engine bay and discovered that the "mechanic" that reinstalled the trans kinked the vacuum hose from the intake manifold to the modulator valve when he hooked it up. I disconnected it and reinstalled it without the kink and have not been able to recreate the event since then. So, I think that I found the problem. Apparently, a kinked vacuum hose has the same result as a bad modulator valve! I will test it some more, but I think I found the problem. Besides, what good is a spirited Mustang without spurring it up a little to get out and run? The engine sounds great and all is good in the Santa Ynez Valley! Thanks.