Here's how I came up with that info- I installed a Super B on my '03, along with the BD manifold. Following some of your posts, a friend is tempted to do your modification, so I found a 351 on ebay, and compared it to the 341 from my '03. After a casual look, the two turbines look the same, but the digital caliper knows the difference. I didn't disassemble the compressor side because I didn't want to fool with that huge snap ring. The 351 also has three studs as opposed to two on the 341, and its flange is thicker, along with the flange on the 600 manifold. He was considering buying a new 600 manifold, but once I doscovered it is a single volute design, that would make it less desirable for a two-volute turbo like the Super B. I haven't taken any road trips with my '03 to verify any MPG improvement, but its driveability is very good, with maybe the tiniest bit of lag. Boost at 65 on a level road went from 6 PSI down to 2, with about a 50 deg. EGT increase after turbo. The only downside is you have to shorten the exhaust system about 1-1/2 inches, they don't tell you that in the instructions. Engine still gets plenty of air, as when I removed the exhaust elbow again to shorten the downpipe, the turbine wheel was soot free (almost bare steel) so I know it's not smoking any. IMO, the aftermarket manifold, whether BD or ATS, is a vast improvement over either stock mainfold. Also, the BD is a slip fit which makes installation easier than the ATS with its ball joint, and it is already drilled for pyro or drive pressure fittings.
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