I see certain wheels offered and tried to find out whaty the differences were, but I haven't come up with any explainations or pictures. Can someone point me in the right direction?

 

TTT

 

Go to http://www.turbocalculator.com

 

That's a question that has long been answered and its gets pretty in-depth which may be why there aren't many responses. Many different wheels have different sized inducer and exducer trim wheels which change the characteristics of pressurized airflow in a turbocharger. Check on howstuffworks.com to really get in-depth.