Source of smoky flavor in salsa? I'm experimenting with making my own salsa. I recently had some that had an interesting flavor, rather smoky. Is anyone aware of what might add this flavor? I'd like to add that flavor to my own salsa.

I don't have a smoker, but I do have a charcoal grill. 

Is there a disadvantage to just adding a couple drops of liquid smoke?
Chipotle chiles, especially in adobo sauce (e.g., here), give an excellent smoky flavor. You should be able to find these in your grocery store in the Mexican section.