After nearly 5 years with RC6, Jeff at RC wrote a new tune for my wagon. Since the engine refresh I've been unhappy with smoke on tip-in and responsiveness at low revs. Jeff made an RC 4+ that accommodates my mods (ported head and Dbilas cam, PD150 intake, etc.). It's a 25 PSI tune but on NA base maps so it has the "softer" accelerator response than the Euro tune. But I won't have to swap ECUs for annual inspection.
Just drove 200 miles home from the Fest and it's a big improvement. Easier to drive (RC6 always took a gentle foot to drive smoothly), much less smoke, and still pretty quick. The exhaust note has changed a bit: I've always had a bit of a drone that starts at 85 MPH or so, now it seems to come in at 80. But the engine sounds quieter (less timing, perhaps), so maybe it's just more noticeable. I'm betting I'll gain a bit of FE, too, based on where the gauge is after the drive home (550 miles on this tank, one tick below half).
Of course if I long for RC6 again I still have it on my OE ECU. But I'm happy.