Car looses power on acceleration.

Things should be tested before you replace them . You could have bought a scan tool and a fuel pressure tester instead of parts you don't need . It could be a loose/broken vacuum line or gummed up injectors . You may have bought some crap gas and a can of octane boost would have fixed it .

Is the check engine light on? If so scan for trouble codes first. Most auto parts stores will scan the computer for free and give you the codes. Then you'll know what's going on! Hope that helps! Jim

The car never throwed any codes, I have a reader myself. Update, even though the cat is practically brand new and only been on the car for maybe 3 months, i took it off today and it shakes like a rattle can. That was the problem.

Exactly, unless the original catalytic converter has very high mileage on it, catalytic converters usually don't fail on their own. The fact that the "brick" inside your converter is falling apart indicates that it was overheated. Misfiring, as F_O_R said, is the number one cause for this to happen. Fix that before you replace the catalytic converter again. Hope that helps! Jim

Oh and one other thing. When you do install the new catalytic converter it must be preheated before you drive the vehicle for the first time after the converter is installed. This is done by starting the engine and holding the RPMs at 1,500 for five minutes. Then you're good to go. Jim