Mixed plug wires?

[Dave Rifkin]

What would be the symptoms of an engine with a few plug wires mixed up? I have a 1969 L46 Corvette that, in my opinion, has never run up to it's potential. I have taken it to multiple Corvette "specialists" and no one has been able to get it to run to my expectations.
My last mechanic performed a tune up and told me that a previous owner / mechanic had installed the distributor off a few teeth. Rather than remove the distributor this person made the adjustment by rearranging the plug wires. (None of this makes sense to me as I would think I would have noticed that car running rough or something).
The latest mechanic says he removed the distributor and reinstalled it correctly.
Ever since he did that the car runs rough when I step on the gas. He told me that the carb needed to be rebuilt so I sent it to Eric Jackson. Eric said that the carb was in need of work so I was hopeful that the car would come to life once it was reinstalled.
While the car does pull stronger it still runs rough when I step on it. I can't help but think that my new mechanic didn't do me any favors by messing with the distributor.
I think he created a new problem but, I need to know how a car would run if one or two wires were mixed up.

I am desperately trying to find someone who can get my car to run like I think it should. I am so disappointed, and frustrated, that I am considering selling the car since I no longer enjoy driving it.

Please help!!!