Well think perhaps I finally resolved my vibrating tire issue on my '92 Camry. Drove it back to Walmart again (45 miles) and this time planned on putting on Goodyear Viva Touring tires and dumping the Goodyear Aquatred 3's. Discovered they didn't have any Touring tires in my size in stock, so rather than tear my hair out again and return again, I decided to give the Douglas Touring Tires a try. $10 cheaper per tire, too. :) 80,000 mile warranty as well. So I went that route. Service Mgr is one of the nicest customer service people I have met anywhere - he has repeatedly worked with me to solve this problem. Walmart needs to clone this guy. Didn't cost me a dime, in fact rebated me $40 since these tires were less, although I had put some 6,000 miles on the Aquatreds. Guess he felt I had been hassled enough.
Drove off, expecting the worst, but discovered that this had finally done the trick (of course, I had to check the tire pressure before I left, since Walmart is notorious for overinflating my tires. Sure enough - 42 in the left front, 48 in the right front, 40 in both rears. So I reduced them all to 35). Now that's a relief - can't even count how many times I've gone to Walmart over the past year trying to figure this out. Now off to Toyota in a few days to figure out what is rumbling in the rear end of this car - expecting to get hosed by the friendly folks from Toyota. We shall see. If they could stop this rumbling, I'd probably see an even smoother ride - in the meantime, I keep expecting the rear wheels to fall off, the gas tank to drag along the ground, explode, and send me to where I probably belong - hell! Ho, ho!