Have 2004 audi 2.0 fsi main fan keeps coming on when moving.

Could be this fancy oil ,like the newer 0/30 multigrades ,try using a straight 40 monograde oil ,you have a pressure problem with the internals and it could be anything from worn oil pump to worn mains ,another trick is too add some winns or STP oil thickener and sell it quick or this will cost a arm and leg to repair ,maybe another engine from a accident damaged car in the scrapyard .

REPLACE NOX SENSOR BEHIND CATALYST...

You need to rest the anti thief alarm.

Check both ends of battery's earth lead.
Remove, clean all surfaces with emery/sand paper, replace and seal with grease or vasaline.
If this is not the fault - it worth doing and eliminates something.
Hope this helps.
Mike

You're going to need to visually inspect for leaks and if no external leaks are evident I suspect your head gaskets are leaking again - check oil for coolant in oil - it will look milky

I am having the same problem on my Audi A4 2004 FSI, lose power whilst driving at speed with the EPC light coming on. Looks like a design fault of some kind with Audi petrol engins, have read a few forums about this but no clear straight answer. Check the link below:

http://www.audi-forums.com/b6-forum/37371-a4-fsi-epc-light-power-loss.html

VW engines intend to do this, even if you pull up at a set of traffic lights it will nearly cut out or go into high rev's. i have an a3 & once driving down the road @ about 50kpm, I lost power stearing for 1-2 seconds, stearing wheel went stiff. Audi are a good drive but needs lots of tlc. One other thing is fuel pump could be acting up a bit.

Have you verified that the power steering fluid is at the right level? If it isn't, you need to fill it to the proper level using specific Audi power steering fluid (it's a mineral-oil-like fluid, NOT the stuff you buy at the parts store). If you've run the reservoir dry and kept driving, it's likely you've burned out the pump and will have to replace it.

Yes according to the dealer they are the same heads..