I bought a 2.5" test pipe on ebay. I'm trying to figure whether these bolt center measurements are right, and if so, where to find a flange large enough to match. The plan is to weld another flange on the downpipe (turbo), which currently has a 2" flange/pipe welded into a 2.5" pipe. It's the only bottleneck I can find (other than the previous test pipe) in my entire exhaust. The flange bolt center looks to be about 4.75", which doesn't appear to be common at all; can't find them on the net. Am I measuring this right? I get the feeling like I'm missing something obvious.