hi need so help i put a decat on my car about 3 mouths ago and ever since the engine light keeps coming on the code is saying my cat is blowing.

But it only happens when it wants to i,e i drove 2 and a half hour to the strip, raced all day and then drove all the way back and no problems. the next day went to a show half an hour away came on so i reset it when i got there and guess what it came on agen on the way back.

any ideas how to stop this i cant see no gabs in the joints and all i am doing to reset it is takin the battory off and putting it back on

please help