[6pack] Carb woes?

[Mike Keenan]

I have a 74 TR6 with rebuilt engine and recently overhauled Webers. I am
experiencing the following problems:
1. hard to start when cold
2. very rough idle at start up, then smoothes out after 30 seconds or so, but
still need to pull the choke out , maybe a little less than = inch to drive
well
3. after driving for 15 minutes or so, the performance degrades, idle drops,
and need to pull choke out to maintain.
4. when  this happens, an especially noticeable change occurs in the exhaust
note when coasting in any gear, especially going downhill...the sound is
noticeably weaker and somewhat tinny, with some metallic-sounding (but weak)
backfires(?), and then often a somewhat louder metallic clunk when
reaccererating (a stuck carb?).
Because the engine seems strong and smooth when pushed to higher rpms when
still, and when accelerating, I'm guessing this is a carb or other fuel
issue.
Any help would be appreciated.
Thanks,
Mike Keenan