I'm in the process of just doing the fine tuning, and wanted to just make sure I'm covering all my bases here.

1.  White Spacer mod - filed to 1/2 thickness of original

2.  Idle mixture adjusted 1 3/4 turns

3.  Rejetted to 152.5 from stock 145

4.  MAC exhaust added

5.  Stock air filter

6.  Stock spark plug

OK.  Just a couple of questions based on what I've done...

I still have just a little residual "pop" or "backfire" on occasion when decelerating.  Not much at all, just occasional.  Would this be the norm or is there still a bit of fine tuning left to do?  If so, what do I need to do?

Pulled the plug and looked at it while ago, looks like a bit of dry black carbon on there, but I really don't think I can go by that as it is the first time I've had the plug out since buying the bike a couple of weeks ago.  Cleaned the plug up, verified the gap and reinstalled until I can get to the store and buy another plug.  

Anything you can read from the plug though based on what I related to you?

On a side note, I went out and saw I had a flat rear tire today.  Aired it back up and observed a leak around the valve stem.  Closer inspection revealed the nut to be loose.  Tightened it down and it slowed the leak, but I'm thinking bad tube anyhow.  Probably will head to the dealer next week and have them put a new tube in as well as a rear tire while they are at it.

When you are refering to the K&N drop in filter, it doesn't have any screws to attach it to the box like the stock filter does it?  I ordered one and the photos showed that it should screw in like the stock one, but there was no mounting hardware.  The frame for the stock filter doesn't come off.  I returned it because I thought something was wrong.

Dang... I had the same thing happen a year and a half ago.  I've also heard of it with at least two other folks.  At least they got the bracket out to me very quickly.  If I remember correctly, you use the stock screw though.