I think Mr. C James nailed it.

Sounds like your catalyst are clogged up.

Hold your hand at the rear of the tail pipe and have someone step on the gas, I bet you don't have much breathing through the exhaust.

I had a customer with this problem, and he drove it that way for a year, well actually his wife drove it, but never noticed because she doesen't know the difference, but he noticed it first time he drove it one day.

I came out, told him what he needed, and he still has yet to get it repaired-go figure.