More Projection stuff

[Fitzgearld, Fredric]

Ok, I probably shouldn't have, but I just ordered the Holley, 502-20, 
open loop, TBI system (its' the digital version of the old analog 
system).  I'm hoping to use it as a base for some experiments I've been 
thinking about.  I also hope to use it as a learning tool.

Questions:
1.  What is the difference between the "502-20" and the 4Di ECM?
2.  Is there a way to make a PC interface for the 502-20 like the 4Di 
3.  Anybody have any interesting bits of information on this system?

Other comments are welcome.

Thanks, 

FEF