Possible vacuum leak?

1988 Astro Van. Engine rebuilt, over 7 years ago, quality job. Never had any real problems other than the peripheral things one would expect to encounter. Alternator, water pump, etc. Lately, however, the engine is cold starting. It starts, and you have to let it warm up really good, before attempting to put it in gear or go anywhere. It will definitely die if it's not warmed up. Lots of engine stuttering. We just did an extensive trip (2000 miles in a week) and along with the cold start problems, we noticed a sluggishness in the cruise control. The cruise is an aftermarket installation (installed many years ago), but once again, has been flawless. On this trip, maintaining constant speed on hills was a struggle. It seemed ok, if you "helped" the cruise with the accelerator just a bit. Also, not when cruising, but when accelerating to pass another vehicle, that the kickdown was sluggish. My mileage on trips has always been 20 or 21. On this trip, my gas mileage was down to 19 and 20. Any suggestions? Thanks. The engine is sound, doesn't burn, leak or use oil. Compression is good, and it doesn't run hot. Transmission was rebuilt about 50K ago.