Carb jetting issues

I have been reading alot of guys running 155 and 165 main jets in basically stock bikes with bolt on stuff. I don't know what to think but here's my story and my dilemma.
My 400ex has a K&N air filter with stock air box/ snorkel setup, a White Bros. E-Series silencer, and I ride in South Jersey. I changed my main jet to a 155 and found I was using twice the fuel and she was bogging on the top end. So I went down to a 150 main and it was running OK with almost normal fuel consumption. I then purchased a Dynojet jetting kit and installed same. The needle is in the stock C-clip position (3rd notch) and the main had the Dynojet emulsion tube with a Dynojet 146 main jet. Shortly after this change I also installed a Pingry oversize oil tank, claiming to lower the operating temp of the engine because of the added oil capacity and the tanks cooling properties. This setup ran well, but on extended rides I was still running out of gas first. I changed the main to a Dynojet 142 and the bike runs great but I'm afraid of being too lean and doing some damage. The bike doesn't break up when wide open and pulls strong, but I notice a louder exhaust note, almost as if I had increased the compression. Give me your opinions...

[JEFF8400EX]

CHECK THE PLUG COLOR

[max400EX]

Yea, put a brand new plug in and if its white after some riding, it is lean. you want it to be tan. black will indicate a rich condition.

[buckeye400ex]

I just talked to a very knowledgable carb guru today. He mentioned something that I guess I knew but never thought of. If you've ever been to a NASCAR race and watched them practice, routinely you will see a car come down the front stretch, at top speed and just cut it off. Coast all the way around pull in and get the plugs checked. I know this because I am listening to them talking on the scanner. Anyway...

They same thing applies to a quad, if you are looking at whether the MAIN jet is right, you need to check the plug when running at 3/4 to full throttle. If you run, then putt around in to your garage the other jetting (needle, pilot) comes in to play and your spark plug color could be affected. So get going wide open, pull in the clutch and hit the kill switch. Pull the plug and check it. That will a better indication of your main jet's performance, too lean or too rich.

Like I said, something I just never thought of, but knew that the NASCAR guys do it. I'm gonna test mine again that way.