Restricted Cat

Today I did a test to see if a restricted cat is what's making my truck bog down on hills.

1996 2.7L 4x4.

First, I unbolted the downpipe from the front of the cat and just left it hanging open. Then, I went and drove up the grade near my house on the interstate. I used 4th gear the whole way, and tried to maintain a constant speed of 60 mph.

First run (Cat disconnected) I had one slowdown to 55 mph/2800 RPM.

Then I came home and reattached the Cat and did the same drive again.

Second run (Cat connected) I had two slowdowns:
50 mph / 2500 RPM
49 mph / 2400 RPM

Am I correct in thinking this means my cat is restricted?

If so, has anyone used an aftermarket bolt-on like this one:
http://shop.advanceautoparts.com/p/magnaflow-direct-fit-catalytic-converter-stainless-steel-23882/22316959-P?searchTerm=catalytic+converters

Any other affordable recommendations for replacements that will bolt right on?