If I read this right,
1.) your bike has 100% stock jetting? And you
2.) Removed your aftermarket expansion Chambers and reinstalled the OEM catalyzed exhuasts.
And your bike now feels sluggish, slower etc..
If that's the case...there's likley nothing wrong at all, You just restricted your motors potential buy a real and honest 11-13 h.p. as it's a U.S. spec emmisions bike. Your bike will run, as such with a noticable loss of grunt,actually a huge noticable loss, from what your used to.
You can run Chambers on a stock jetted RZ with no problem whatsoever at your elevation, and never worry. Re jetting would have been ideal, but not necessary.
If you were/are attempting to go back, to stock or if in fact the carbs are untouched..I'd leave it stock everywhere.
If I was interested in a stock machine, I'd want absolutely untouched OEM bike.
There's a possibility that your OEM pipes are partially clogged, due to catalyzed material breaking down after 30+ years? or oil/carbonsaturation if they were used for many miles..I'm thinking out loud, but I don't think you could clean them without causing damage to the existing material? But back to my 1st thoughts when reading, the stock pipes are very, very restrictive you just may be hitting that wall. It's something you absolutely would notice, as it's a massive decreases in performance everywhere in the powerband. Your going from high 50s in h.p down into the mid 40 h.p range..it would be a total buzz kill as far as performance.
Banshee (Baja) race bike, Lonestar A-Arms, dual 9" L.E.Ds, FMF, Toomey,19cc domes, IMS tank, run flats.
96 GSXR SRAD, Future Yoshimura Lucky Strike rep.
85 custom Tri-Z
RZ/YZR track bike(project)
86 VFR750 RC24 Merkel replica (project)