Stuff a banana in the tailpipe, romp on the gas and hope for the best.
All kidding aside. Sounds like you do have a nest inside the exhaust. At least you now have a story to tell youngins.
Is that still old gas inside the tank? If so, get rid of it. No sense continuing to suck old gas and crap into the carb.
Carb, rip it off, open it up, drop it in a coffee can full of kerosene. Soak for a week.
Now that I think about it, burned acorns only means one thing, those bad boys are WAYYY up the exhaust. Exhaust gas shouldn't be getting that HOT inside the muffler to cause wood to start burning. But, thats IMO.
1997 Pontiac Bonneville SEi-SCRAPYARD
2000 Chevrolet Blazer LT 4X4 4.3L
2002 Chevrolet *-10 LS Ext Cab 4X4 5.7 V8