MPG trouble and B-12 chemtool info + MPG Tips?

[kaput]

Hi,
I have been noticing that my bike has been getting really low miles per gallon (45mpg) and I want to do something about it.

I have already regapped the spark plug and (this may make certain people cringe) took part of the restriction off of the air filter.
I am guessing that my filter is dirtier than it looks and not letting enough air in. I have a new one coming in tomorrow hopefully. I suspect this will make a sizable difference, or hope at least.

I actually got the little GZ up to 80 miles per hour on the freeway yesterday wich was a big improvement over my 73-74 record before. I have also am up to 52 mpg which is better but nowhere near the 70-80 mpg everyone here reports.

I am 205 pounds and I also push the bike pretty hard so I suspect that has some bearing on my low MPG but figure I should at least be getting 60mpg pushing it as hard as I do at my size.

So today I filled the tank using the 3.7oz of B-12 chemtool. How many tanks should make it clean?

Also do you 70-80 mpg small people ride super conservatively? Can some folks my weight report their MPG?

I could see adding 10mpg by riding alot slower but what fun would that be

Any MPG tips?