"Can anyone else elaborate on the origins of the over axle kit?"

This happened more than a few years ago. The last Volvo cat-back I purchased from Volvo for a 240 cost $204 with my VCOA discount from Herb Gordon down your way in January 2001. The 271421 was under axle just like the one I was replacing. Before that, in May 2000, one cost $261. That same time Starla sold theirs for $119. I switched to Starla after learning Volvo's warranty did not extend to the pipes, only the mufflers.

It was shortly after then the Volvo dealers no longer stocked the under-axle kit, explained to me as a space-on-the-shelves move, claiming "either type fits." For a time I was stuck with one of those over-axle resonators on my shelf, no pipe to match.

In the intervening 18 years I've used many Starla kits. The price goes up and down; I cringe at paying more than $110 and know I've found them for less than $90 without looking up records. I don't pay much attention to the debates one reads about exhaust restriction by the squashed under-axle pipe vs. the same restriction from tight bends out of the resonator. We don't race. Always have a spare kit on hand (with 5 daily driver 240's in the family) as I don't want to wait for shipping when an axle pipe rusts out.

One item that's worth getting from Volvo is the rubber ring used to hang the resonator. The 91-cent aftermarket rings don't stretch far before snapping, but those I've received from Volvo and have their part number molded in are worth six times that price.

As for Bosal, I've not ever found/used a Bosal cat-back kit, but have on many occasions used Bosal cats and Bosal head pipes. Mixed results on the head pipes, but that's another story.


--
Art Benstein near Baltimore

It may be that your sole purpose in life is simply be kind to others.