I need some mechanical help.

My daily driver is having revving and stuttering problems when driving long distances.

Its a 95 200sx with the 1.6L engine with 202,000 miles on the clock. Everything was running fine until yesterday. I live a good 40 miles from work. When I got within 2 miles from my job I noticed the car was having problems and would not rev past 3500 rpms. When I left work everything was fine. Then I got about 2 miles from home and the same thing happened.

I'm about 70% sure its the catalytic converter.

Any suggestions before I put any more money into this thing.

Thanks
Z