Exhaust Tuning

I have the V&H Street Megaphone 4 into 1 exhaust system on my KZ750. When I bought the system years ago, I also got their exhaust "tuning" kit. It consists of 3 reducers that slip into the collector where the muffler attaches. The collector is 2" in diameter and the kit has a 1.25", 1.5", and 1.75" reducer. Anybody else use or have experience with this kit?
The bike is stock currently except for the exhaust. I slipped the 1.5" in the exhaust for more midrange and have been riding with that for a few years. I am planning on going to pods and rejetting the carbs for the 2" exhaust (I have posted on the carb forum for the changes required for the carb jets having pods and 4 into 1 exhuast system). The bike runs out of breath above 7500rpm and that needs to be fixed.
So, any thoughts on the kit?

Don't

What do you suggest I should do for now? I take the "don't" as do not rejet carbs and put on pods. Am I correct? Should I run the exhaust at 2" or use one of the reducers to get closer to the stock exhaust flow?

My KZ750 has the stock motor and Keihin CV34 carbs with the N01A needle jet. I have the V&H 4 into 1 and a UNI foam air filter in the stock air box.

I would suggest putting on the pods, leave exhaust as it is for now, run it with the pods and see how it runs. Run it long enough to get a good color on the plugs and jet accordingly, just putting pods on my bike, stock exhaust I went from a 92 main to a 95 and it is spot on, also a .5 mm shimm under needle. most exhaust mods i have done has required jetting also so suggest jetting with the pods first so you can get a better feel of the performance changes as you go, if you do everything at once, it is more difficult to get it tuned

In my opinoin, you should keep the stock air box.

Just an update.
I pulled the 1.5" reducer from the exhaust and changed nothing else. I took the bike out for a 40 mile spin and there is a noticable difference. The bike runs better without the reducer with power from idle to redline. It used to stagger above 7500rpm. The midrange does not feel as strong but the overall powerband that I am shooting for is better. Thanks for the help. I may move to the jetting and pods, but for now it's less wrenchin' and more riding.