Little Help!

[1STtimePRo'71]

So it's been raining here in Minnesota for the last few days and I havent fired up the old girl for a few days. During a break in the rain today I ran down to the gas station to get some munchies. She started up just like normal, I let her warm up for about a minute and then I took off. I always start in second, but as I hit third gear and eased into the throttle she sounded like she was trying to puke her guts out. It was the weirdest thing. It sounded like it was trying to cut out or something. The really wierd thing was that I was coming from under my shifter.
If you've ever lit a bottle rocket and held it until just before it blows, thats what it sounded like. ppffffffffftttttttt. Of course I let off the gas when I heard the noise, and kept on all the way to the station in 2nd(really not that far of a drive). When I started back home I tried third again, same thing only this time it was louder and I swear I smelt something smokey. I looked behind the truck, no fluids, no smoke, nothing. What the hell gives??!! Any ideas