If the Thermac is stuck it may do that. Under normal ops, the air cleaner gets its air from the heat stove only when it's cold out. If you were going to have to lose anything, for me, the silver heat tube would be the one to go. Once warmed up, the Thermac closes off the heat stove and air is entirely drawn in through the cold snorkel/air intake duct.
BlueCalais79 - Glad that the part fit your 79 to where you like it. Function over form usually wins the day for a daily driver. Depends on how correct you need it to be. I had no doubt it would fit the air cleaner and scoop, it was just a matter of how much extra you'd have and how well it would clear the alternator and fenderwell. I still haven't done a head to head comparison on the two numbers yet, but there is a reason there were 2 different part numbers. It very well could be one was 3/4" longer than the other. GM did weird junk like that.