Where is the engine number located on a kawasaki zx10r 2006 model

The model number and serial number on your Kawasaki Engine is located at the rear of the engine on the engine housing

The average MPG is in the mid to high 30's, but is also very dependent on your right wrist.

if it has carbie/s then check for a faulty float needle and seat
may be a simple thing such as a hair stuck under the needle as it is flooding

READING WRONG TOO IS ACTUALLY A NUMBER OO

As long as you get a muffler that is comparable to a stock muffler then it will have no effect on the performance. Most aftermarket companies make stock mufflers that would fit your bike though it would likely be cheaper to just replace them with stock kawasaki pipes.
As to replacing them, using an impact wrench will make removal easier and be sure to use a new clamp even if the old one looks good

My research shows that the damper also fits ZX10R (2004-2005). I would use caution when crossing bike parts. The part numbers are the same with a suffix letter different. This indicates a variation in the part. So although it may bolt up and perform the same, there is some difference.
Ride Safe.

http://www.superstreetbike.com/how_to_installation/0904_sbkp_2009_kawasaki_zx10r/photo_15.html

Probably not charging, your bike has an alternator just like a car. Get it checked.

in shop visit weeklyvisiters.blogspot.com

The frame mounting points are completely different. A zx 636 frame wraps around the motor where as a zx10r frame goes directly over the motor. That's how they keep the zx10r nimble enough to feel like a 600cc sport bike. But in this day and age if you have enough time and money you can accomplish anything. Honestly it's just easier to sell your 6 and buy a 1 liter.