I concur about the OVP being the source of warm start problems. The first thread I ever posted involved a warm start problem, and replacing the OVP solved it.
The rough idle problem can be caused by a number of things, electrical, vacuum, or fuel system. That will require a bit of top-down stepping through each of the systems to rule out causes, otherwise you end up just "throwing parts" at the problem.
2009 ML350 (84K) - Family vehicle
2001 CLK430 Cabriolet (71K) - Wife's car
2005 BMW 645CI (124K) - My daily driver
2012 Mustang V6 (60K) - Daughter's car