We use a tracking code as well through ASP, and haven’t seen any problems, though we are still in the Sandbox, so it’s hard to really say for sure. Definitely no problems ranking on Yahoo though.
The key to Yahoo is to get as many links as possible, sitewides do very well in their SERPs for instance, while they are devalued in Google. Also, your title and on-page optimization seem to count for more than they do in Google.