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The Super Pros have a different merge collector setup that maximizes low-end torque as well as a 3" collector setup that mates with 3" cats (or ORP's, if desired) and a 3" X-pipe which either stays at 3" or reduces to 2-1/2" at the catback flange. The Streets reduce from the 3" collector to the stock 2-1/2" that runs through the cats/ORP's to the flange that mates with a 2-1/2" catback. The 1-7/8" Super Pro's have a distinctive look that is very different from the Streets due to the larger primaries and 3" setup. I have installed both at one point or another. I currently have a set of 1-7/8" Super Pro's that I shoould be installing soon. Sizing up to the 1-7/8" Super Pro's is what changes the look from the other 1-3/4" primary versions.
A pic of the Streets from an ad posted by the vendor I got my Pro's from.