She won't idle...any ideas?

[briarpatch]

Last night I replaced the leaky exhaust and intake manifolds without a hitch on the ’70 C10 with 250 L6. Exhaust doesn't blow into the engine compartment now and it sounds better. The problem I have created is the engine won't idle now. It just dies out if I let up on the accelerator. Nothing seems to have changed with the carburetor, or anything else that I can see.

Any ideas on what I should be looking for?

Thanks!