Its possible the pipe is a metric product, but the reading on my calipers wasn't an even-metric or an even-decimal measurement, so I can't be accurate.
I measured a spare OEM header I have in the garage. My calipers don't get inside the heat shield cleanly and I don't have time to screw with that (sorry) however they got in to their tips and looked like they were past the radius of the pipe OD. Anyway the raw pipe OD (not near a weld or flare) measured 1.498" on the straight before the collector and in the bends it's a hair less due to bending (1.494" worst case). It could be 1.5" pipe, or 38mm.
awsome, thanks much! i think the stock header will do perfect for the "beta" version header for the turbo. just may be one bend short, but i think the rest of it will be perfect for starter! if not im definately going to be using the flanges at the very least. but thanks again.
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