'96 E300D, sluggish performance, unstable idle, noise

[E_S]

Just bought a '96 E300D (OM606 non-turbo).

Some small issues:

1. The car feels very sluggish. Yes, I know it's not a fast car by any means (I used to have a E250D!), but it feels too weak to have those 136 hp. Even going uphill on the highway at 60-65 mph demands "flooring it" to maintain speed. Fuel lines seem OK without bubbles.

2. Rattling noise on cold engine. Not valve lifters, it sounds a lot like the tensioner noise, but pushing on the tensioner using a screwdriver does not make much/any difference to the noise. Does the OM606 have the clutch alternator pulley that can cause noise too? The noise seems to go away when the engine warms up.

3. The car idles stable - but when the AC compressor is kicking in, it will surge for half a second before stabilizing again. Same goes if quickly giving the throttle a "blip" when it goes back to idle position.

Any advice for those three issues?