Sorry for the delay in looping back.   Time has been very tight and I am on extended travel..  Right before I left for travel, I decided to clip my tev spring. I had checked everything and there are no leaks, no suction near the intake boot or anything.  In thinking about it, I became convinced that there's something wrong with the tev system even though I changed the diaphragm valve.  So to get ready I had ordered from ebay a kit that had not only two extra valves but two extra springs.  I was going to keep the original and clip one of the eBay one loop off to see if it has an effect.  I took the cover off and put a wire down the side orifice that provides the vacuum for the valve to make sure that was cleared.  When I brought the ebay spring out to clip it, I was shocked to see how much longer the spring inside the carburetor was compared to the ebay kit.  It was almost double the size and made with same gauge wire.  This means that the valve was being kept shut at a very high force!  So I immediately put in the much shorter ebay replacement spring since the valve was already replaced and went for a test ride.  Wow What a difference!  The bike still after fires but it is significantly less and it is not as sharp or loud. Dare I say it , but it's nearly tolerable now!  So basically , one of the prior owners really messed this bike up with leaky exhaust upgrade, smaller than stock jets and a non-stock spring that basically eliminated TEV function. Ugh.  I appreciated all the comments and suggestions but I guess you were probably thinking that I was hearing normal popping and wondering why i'm being so picky.  I will admit that I am picky , but now i'm certain I was not hearing normal popping.  Anyhow, I am so much happier with my bike now..  Thank you everyone!

That is great that you found the issue - I did suspect that perhaps a stiff diaphragm was contributing to your problem.....I never anticipated somebody had modified your spring.

I have often wondered if the use of E10 fuel will increase the noise.  The TEV is likely a bit less effective as E10 needs a bit more fuel in the fuel/air mix to burn properly.  I have never looked to see if there is a way to slightly increase the amount of fuel flow through the TEV circuit. (I don't use the stock carb anymore on my bike....but it did run well when I did).