I think it's something Jethro put together when his truck broke down.
Funny.
Looks like a turbo on the left side, and at first I thought that aluminum box on the right side looked like an intercooler to cool the intake air, but intercoolers need cooling airflow, and I can't see that here. Might be just his way of routing the turbo'ed intake air into the engine.
That red contraption low on the right side is probably the wastegate adjustment, as someone else mentioned.
The filler cap on that crude gas tank is interesting. I don't know what he might be putting in there - maybe it's just for effect.
What's a real eye-opener is that wing-nut holding the rear of the fuel tank down. That'll do a number on the jewels if he ever goes over it in a forward direction.