Re-tune/flash necessary with full exhaust upgrade?

[Siggy Javotnik_imp]

"BUT I found it ran a tad rich"
That's counter to what I'd expect, seems like it would run lean after installing aftermarket exhaust.

I had the same thought -- freeing up the exhaust would be expected to lead to a possible lean condition. However, as a fellow Yosh pipe owner, I don't think the can makes a huge difference to the air-fuel ratio. I like the Yosh because it SOUNDS so sweet -- not obnoxious, but just...right.