Is it normal to have to get into the throttle half way or more for the car to begin pulling away from a dead stop?

I just got this car on Saturday so I don't know how a normal 86 300SDL reacts to throttle input. It seems to need way too much pedal to begin moving. And even when I'm cruising along at 30 mph I'm still in the pedal close to 50%. When I get up to highway speed, it seems to take less throttle input to maintain speed. 25% of the pedal will keep me cruising at 70 mph. Might be worth mentioning that the first 30 seconds of idle on a cold start are pretty loud -- 18-wheelerish.

What I've done:
Looked at the throttle linkage for lube issues. Looks great and moves well by hand.
Checked clearance of all pads on rotors.
Replaced the first inline fuel filter and tossed in a can of Chevron's system cleaner (love their Techron on my gasser!).

Next:
I'm waiting on a delivery of the can fuel filter and the other inline filter. Also getting some D-purge in that same shipment.

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