are you throttle happy???

Whatever you did to the stock muffler didn't work.
You might have to get an after market replacement.
I'm partial to the SuperTrapp because it is adjustable and can be dialed-in to the jet you have chosen for the carb. I used the Dynojet kit to jet the carb.

The Gods don't like the Dynojet kit because they say it is too expensive, $70. The kit simplifies the white washer issue. You use the stock washer unmodified, but Dynojet provides a new needle with different grooves.
Their instructions make the mod simple.
I don't know if their jet numbers relate to Suzuki jets numbers, I suspect they aren't related. Also, the Dynojet needle taper might be different from stock.
I'm happy with my Dynojet mod. I just love rolling that throttle open.

Another thing I have suspected reduces my milage is just lack of use. If the bike sits a week between rides, the fuel will evaporate and escape at the cap. Make sure your cap seal is good. I noticed my milage was bad after I went on vacation and the bike sat for 3 weeks.

On the intake side, make sure your air filter is clean.
I prefer the K&N air filter. It has a better seal to the air box, and it improves power at higher engine speeds when the engine demands more air. I suggest however that rather than reoiling this filter, throw it away and get a new one after 10K miles. Why oil on top of old captured dirt?

I'm on Social Security. You're paying the bill!

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It is still possible the exhaust could cause backfiring but usually only if it's been removed (or loosened and re-tightened).  A leak in the exhaust can definitely be a culprit.  I don't know how many times I retuned my carb before I finally replaced the exhaust gaskets.  The gaskets were the fix.

I reported the backfire not to complain but to indicate it's npt rolling down the road dripping gas out the back. My current & loudest whine is about the under 35 mpg.

THough, if changing the pilot jet to a 55 would yield a better ride I would consider it for sure/

I just want a quick ride that still gives decent MPG, anyone got the mods that accomplish that?

Thanks to all for the input. I have never loosened the muffler bolts & haven't dropped it so I would be surprised if it is that. I can (& will) look at the joint & see if there's any soot tho.

Just as an afterthought, you might also look for a small leak.  I found that the Amal carb I bought had a dual banjo fitting instead of a single and one side had been "capped" with a rubber cap of sorts.  The problem was that the cap used was not a petroleum resistant rubber and it began leaking.  For a while it was drops at a time and basically only when riding because of the vacuum-actuated petc0ck.  It was enough to mess with my mileage and yet go unnoticed because the drops were blown away during my ride. It got worse over time.  I once saw a drop on one vent tube and went off into checking my float, etc. but found nothing.  It turns out that capped fitting is above the vent tube on the carb.  Eventually it got to where it was dripping when I stopped and I saw it.  I replaced the banjo with a single (shipped from England) and all is well.  Anyway, a leak in a fuel line or at a banjo fitting or inline filter can make a difference and can go unnoticed for a while.  Just a thought.