1994 Ford Explorer-Catalytic converter causing sluggishness?

Make: Ford
Model: Explorer
Year: 1994
Engine Size: 4.0 L V6
Other: 4WD Eddie Bauer
Mileage: 153,000

I cannot provide the code but here is what I do know.

I have a check engine light.
I brought to shop.
They said the code indicated it was DPFE sensor.
The shop replaced DPFE sensor (1 hr diag+1hour labor+187.90 sensor part).
I picked up explorer, drove home, and check engine light comes on again.
I brought back to the same shop, and now shop tells me that it is the catalytic converter exhaust system. He said "Sucking alot of air in, but not 'farting' it out" thus the cat converter as he said.

Is it possible to have the cat converter give a car sluggish perfromance? Will not shift into higher gears. It sometimes does if u 'baby' the accelerater.

He ruled out the MAF, which is what I thought it may be. What other possibilities for the root cause? Historically, what has been some examples of the root cause for my symptoms? He said that it is definetly not the transmission or MAF.

Any ideas about the cat converter (sorry I don't have code, but the shop swears it is the cat converter, but they dont do exhaust work. So I have to take it somewhere else).

Is it possible for a catalytic converter to cause this problem?