3/8 vs 5/16 fuel lines
Having never used one, does a thermoquad have mechanical secondaries or vacuum?
The quick answer is yes. lol It's a hybrid. The base plate is mechanical. When the throttle is moved to WOT, all four open. The carburetor top has a vacuum operated adjustable air door that regulates air flow through the secondary venturii.
@sorewrist1 what I would do regarding the fuel line would be to leave the 5/16 line in place, UNLESS you are planning on replacing it due to rust, kinks or some other physical reason. Then I would go ahead and make the upgrade to 3/8, since the lines are "about" the same price. 5/16 line will supply 500 plus HP. However, it certainly will hurt nothing to go to 3/8 if you are replacing it "anyway". That said, I don't think that's your issue.
If all else fails, I would look at the float level. There are "several" float settings for different applications depending on performance. I always set dead center of those specs. It could be that as hot as it sounds your engine is, the float level might need to be raised. It's really not a bad procedure to do. If you do "everything else" and still no luck, I think that is what it will be. I'll be more than happy to walk you through it on the phone, OR if you want to send it back after you determine that's what it is, I will raise the float level for you and reimburse you for shipping and ship it back. Just let me know when that time comes and I'll be glad to help however you want.
...and thank you for the kind words.