1997 Stratus 2.0, 154k

Replaced catalytic converter due to CEL and P0420 code. Catalyst efficiency is now OK but the cat leaks on the manifold end. I have taken this off and put it back on but the flanges don't seem to be parallel to each other. They don't make OEM cats for this car anymore ao I bought an aftermarket one from USAAutoParts.com. Seems to be pretty close to the original when doing a side by side. The cat came with a (composite?) donut that goes on the manifold side to mate the two pieces together.

I dropped the exhaust on the other end, tried to align the flanges as best as I could and tighten the bolts, but it is still off. There are springs on these bolts as well. The bolts have a shank on them that seems to bottom out (bolt is tight) leaving me wondering what these springs actually do. I need to have this thing not leak so I can get it through CT emissions this month. Any ideas on how I can stop this leak? Thanks!