speed of PWM ?

I read that the The frequency of the PWM signal is approximately 490 Hz

can this be made faster ?

is there a shield that operates at a faster frequency ?

can this be made faster

Yes http://www.arduino.cc/playground/Code/PwmFrequency

is there a shield that operates at a faster frequency ?

To do what?

cheers for the link

it is to control a fuel injector,

its a shame you loose the time functions

can two boards be connected togther to one does the timing and one does the pwm ?

can two boards be connected togther to one does the timing and one does the pwm ?

Yes in any number of ways. It depends on how fast they need to communicate with each other. You can use:- I2C SPI Serial

ty

is there a shield / frame that allows you to plug them together ?

is there a limit on how many can be connected ?

No and no

do you daisychain them together with a ribbon cable to get them to work together ?

You can generate PWM without loosing the time functions. You should take care to use only PWM that does not rely on timer0. Then the timer and PWM will not interfere at all.

ty

do you daisychain them together with a ribbon cable to get them to work together ?

I2C - yes
Anything else - no

With an UNO just pins 5 and 6 use the same timer0 for pwm. As has been said you can change the timer settings for timer1 and timer2 without losing the arduino timing functions.