Hey there I’m trying to install my test pipes but I noticed that the bolts that are holding the catalytic converter piping to the header manifold piping looks welded on by previous owner. The bolt head is smaller than the bolts came with the test pipes so I assume he improvised when he didn’t have the right sized bolts and welded on smaller bolts. I was thinking to use an angle grinder to try to remove it but I’m not sure how it will turn out. A shop quoted me approx $180 CAD for labour based off the pictures. How should I approach this situation?

(The cats were stolen)

 

Yeah I would cut those bolts off, probably easier with a sawzall, once the flange is removed drill out the factory studs and use new bolts. I wouldn't bother trying to extract and reuse the factory threads with that much corrosion. Much easier to just cut/drill and use through bolts.