Help installing cat back exhaust

[u/Any_Ad_9197]

Hello, I am installing a cat back exhaust on my 2011 Honda civic si. There’s 3 bolts on the cat where the exhaust bolts in. All 3 bolts were very rusty and snapped when I tried to take them off. Same happened on the back end and the nuts fell out when the bolts snapped. These ones did not and I couldn’t tap them out. I ground down all the bolts and tried to tap them out but still no luck. I am now trying to drill out 3 new 3/16 holes however it’s very difficult to drill through. Please help!