I've got 2 questions about a '96 Suburban I bought in CA and brought to MN
last year and all responses are appreciated.

My truck vibrates (bad) intermittently between 60 and 70. It'll run for 30
seconds vibrating like nuts and then it'll run smooth for 10 minutes. Speed
changes seem to affect it. I've had it aligned, there's nothing loose on the
front end that my mechanic or the guys a Tire America (2nd opinion) can
find. Tires are balanced. Anyone seen anything like this?

Also when I start it in the cold it makes a rattling, hissing, clicking
sound under the truck right in front of the cab. No one can find this one
either. Is it possible that the CARB stuff is causing this in the cold
weather?