losing power when going 65mph

I have a 1995 Ford Contour with over 102,000 miles on it. The problem started when I tried to get my car smogged. I have changed the battery and the alternator and the battery light stays on. The check engine light comes on but soon disappears after a few seconds. I can enter the freeway okay but then when I try to get the car up to 65 mph it loses power. Is the catalytic convertor out or is there something else wrong with the car? I had no problems with this car until I tried having it smogged at at test only place and then everything started going out on it. Any suggestions with what is wrong with the car? Thanks.

Could be a clogged cat. Have you had the cel code pulled?

Could be a clogged cat. Have you had the cel code pulled?

Thanks for the suggestion. My brother thought it was the catalytic convertor, so he bought one for the car and took it to the shop to have replaced.