I have GERD and slow colonic transit with a suspicion of mildly delayed stomach emptying that wasn't caused by diabetes. So I can relate just a little.
There was a good thread about gastro-p recently by
@Anaelena who knows a lot about it, and others with it also posted.
I also recently came across this medical paper about it, which I found interesting:
http://www.motilitysociety.org/clinician/manuscripts/parkman_camilleri_anms_aga_gastroparesis_09.pdf
I'm still working my way through reading it (the more medical terminology the longer it takes me). But if you want to discuss it I may be able to help.