As suggested by Cleeves, check your throttle linkage goes all the way to the stop on the IP when the accelerator pedal is pressed to the floor. If the rods are out of adjustment or the pivot on the firewall is wasted, you won't have full travel on the IP. If it seems to accelerate ok, it's unlikely to be a turbo issue, steady-state cruising only generates a small PSI boost state anyway, so you should be able to do in excess of 70 even if the turbo were fully non-functional - it would just take a while to get there.

Cold starting is most likely to be glow plug issues as mentioned above. It could be one or more of the plugs or it could be the strip fuse has a crack in it. The compression numbers aren't terrible, but certainly lower than I'd expect for so low of mileage. Definitely adjust valves. My SDL had compression of 360 on one cylinder and 380 on the rest. It still started fine even if sat outside in below freezing temps overnight.

__________________
Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]