APR Stage Two with my DP

Is there any cost savings in going to their Stage Two and supplying your own catted dp?
I understand APR will charge for going Stage Two if it's someone else's hardware used.
If you buy during their sale time, I'm not sure there's any money to be saved.
Thoughts?

I don’t know if I’m understanding this correctly...
To go stage 2 from stage 1 is $174 (let’s say with your downpipe) otherwise it would be free, but the APR downpipe is like $650 (I don’t remember exactly right now). So yes I’d say that you will save money providing your own (cheaper) downpipe and paying only $174 for the software.
Somebody please correct me if I’m wrong.