From a performance standpoint, which one has more potential if any, the 3.5l or the 3.0l? Any other differences or advantages of one over the other?

At stock settings the 3.5L will pump more fuel but 3.0L will revv higher.

The only difference between the two is tuning, they are the same pump otherwise. 5.5mm plungers in both.

Is the cam in both the same?

In simple words you can get an ip from a 300d to behave the same as the ip from a 350d and vice versa.

Exactly.

Great, thanks for the help.

OK, I got me a 603 IP to play around with and I have a few questions... I've dug around and found lots of nice pictures but nothing that describes the parts of the pump.

So, here's one side.

What's the mechanism on the back/side with the black connector? Is the yellow cap covering the fuel inlet or something else?

http://i3.photobucket.com/albums/y71/kartek/Mercedes/f0c12dbe.jpg

And the other side.

What's the red plastic connector? What about the yellow cap? What's the black plastic connector on top?

http://i3.photobucket.com/albums/y71/kartek/Mercedes/a5d55add.jpg

O.K.

The octagonal black plastic looking device with the red covered center is the
locking device that makes sure the pump is at what could be called TDC.

I think the Yellow plastic cover (round) on the left hand side of the pump
(If it were installed on the engine) is the fuel intake?

The yellow plastic cover on the right hand side is fuel also (but I don't know
how it fits in or on what model.

The Red and Black plastic devices ,one on the back of the pump,one on top
of the pump are the Idle control and some other actuator(BUT I cannot
remember which is which)

If you PM GSXR he'll "Know All"

The green "what is this" is the vacuum control valve ("VCV"). It modifies vacuum from the pump and sends it to the transmission. The idea is to model a gasser's intake manifold vacuum, which is what the tranny expects to see. It governs the firmness of the shifts.

"Another fuel input" is the fuel input. "Fuel goes in here" may be used in other applications but in every Mercedes diesel I've seen it is hard against the block and so unused.

I think the red plastic cover is an idle speed control, part of the "Electronic Diesel System" (EDS).

The black thing "What's this" would then have to be the rack position sensor, which tells the EGR computer and perhaps other things how much fuel is being injected into the engine.

Jeremy

Thanks, that helps a lot. If I adapt this to the 606, I won't need any of the electronic controls I reckon'.