Car makes loud noise when accelerating at high speeds?

My car is a 98 Honda Accord with 151k miles. I had this car for couple of years. A year ago, i had a check engine light came on and several days later, my car started making loud roaring noise when driving at high speeds. Accelerating feels weak. The higher the speed, the louder it gets. When i got the check engine light code read, it says something about "CAT" and emission controls. I don't remember the code now. I drove the car few days a week since then but now i want to repair it. I want to know what could be the problem? Catalytic converter failure perhaps? The noise seems to come from the centre of the car, not the engine. The car run fine under 40MPH speed but gets louder the higher the speeds. If i was driving at 65MPH, its so loud that it's hard to hear other passengers talk in the car. Any ideas?

I don't want to pay $100 for simple diagnostics dealers ask for. I want to know so i can repair it in a cheaper shops.

Symptoms:

Loud noise at high speeds.
Loss of power when accelerating
Check engine light.

Your cat probably has a hole in it.

It could most likely be that you need a new catalytic converter or muffler or both. Prices vary on both but if you get a new catalytic converter you will need to get 2 new O2 sensors as well