Fast Idle in Cold weather

[Murphy IRE]

One more thing to add to my list. The tach isn't hooked up (PO), so I can't tell you how fast, but it does vary. The first time was really fast and I had to switch it to an empty tank to shut off, so I keep that tank empty (I have 3). I pulled the carburetor top off and checked for junk in the bowls - NOTHING -perfectly clean. I put it back together and it was better. This week it happened again (not as fast) but all day. I put it in neutral and hard tap the peddle/throttle and it does come down, but it is still a little faster than in hot weather. Should I start looking for vaccuum leaks? Any thoughts or suggestions? Rebuilt 400 sb with an Edlebrock 600

Murphy