A few possiblities to look at;
Check the fuel pressure and the fuel pressure regulator.
Check for vacuum leaks.
The camshaft position sensor could be affecting the ignition timing, as well as the cranshaft position sensor. However the fuel ijector timing is actually what is called a, "Pulse Length". This is how long the injector is open and squiting gas. It can be affected by the cma/crank position sensors if they are failing, it all depends on where the injector driver pulls its signal from, sorry I do not have a manual on your car as we only have USA based vehicle manuals, but if it is not one of those throwing things off, it may be that the timing belt has skipped a tooth and is affecting both the fuel management and the ignition systems.
The injector pulse length would be causing the gas mileage to be very bad and could casue rough running. However the whistling noise may be another issue all together.
I am including a link to a walk through tutorial that goes through what causes whistling noises.
I think you should go thorugh it, get the fuel pressure checked, check for vacuum leaks and get the reulator checked.
Then if you are still having trouble or if you need any help along the way, I will reply to your question ASAP.
Here is the link;
Tuesday, November 8th, 2011 AT 9:59 PM