Can I fit a K&N air filter to my 1998 Audi A4 1.8 Turbo Sport? If so how as there are sensors ontop of the airbox (airflow sensors) and if I disconnect them ther engine wont run. Help?

 

Put a K&N panel filter in the air box, or strap everything down once the cone setup is on.

 

^ That. Pre-'99.5 North American B5's will run on just the O2 sensors. If you really want a cone for the nice sound it makes, then get a K&N cone with a 3" (I think) opening. As for the sensors that clipped to the top of the airbox, I just ziptied them off to the side. I used black zipties because I'm not a ricer douchebag.

 

It's a 2.75" ID cone filter that will fit onto the stock MAF.

Ideally with a cone filter you'll want to run a heat sink on the ICM, and have a good sized heat shield to prevent heat soak from the turbo, like this:
BlinkTek Design (find the one for your car under Products)

 

You can also PM Meloman. I think it's either him or tware that makes heatshields.