I have not tried the glove test but read about it last night. It's to rain all week here. If I can dodge the rain drops, I'll check the glove test, nipple and other things. Vacuum lines seem to be intact, but I know visual inspection isn't enough.

All 5 plugs and one bad coil were replaced about 5,000 miles ago. Timing belt and serpentine belt were replaced shortly after 120,000 miles.

Curiously, the mpg did drop after replacing a fuel pressure sensor on the fuel rail. But we're not having the problems the old sensor gave us, like CEL and loss of power at speed on the interstate - scary! Maybe it's a wrong assumption, but I am assuming the new sensor is not at fault for our current decline of mpg.

Also got new tires right around the time mpg started dropping, but it's dropped much more than I would expect for new tires. Plus there's the whine that wasn't there before.

Thanks all for the responses. I appreciate your time. Wish I still had a garage, dodging rain drops ain't fun while wrenching.
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94 944 na 319,000 and rolling; 05 XC90 2.5t AWD for the wife; 97 Chevy Suburban 3/4 ton 6.5 diesel daily driver; 92 745t beautiful condition (sold); 88 764t failed experiment (sold)