Just curious. What's the elevation where you live? My SD is a real dog at higher elevations, just as you describe, but fine near sea level, and it has fresh engine, IP, ect. Maybe your new car just doesn't like high elevations. I'm still learning about what can be done about this. From what I've seen guys here talk about, it's the ALDA adjustment.

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past MB rides:
'68 220D
'68 220D(another one)
'67 230
'84 SD
Current rides:
'06 Lexus RX330
'93 Ford F-250
'96 Corvette
'99 Polaris 700 RMK sled
2011 Polaris Assault
'86 Yamaha TT350(good 'ol thumper)