does a regular i40, but with all option also have air suspension on the back like the M50?

It does.

 

Seems a good comparison. I have driven both, the e40 feels similar to my recollections of my previous F30 330d sDrive. But, slow compared to my present F31 340i sDrive.
You will loose AWD but performance will be compatible. Given to i4 weight I felt the acceleration of the e40 was equivalent to to 30 engines and the M50 was 40 engines plus.

 

Thank you. But doesent the 40 has way more instant power?

I actually never drive in sport mode (430D) because its simply to loud and I actually dont even like the diesel sound.

So, how many touque per kg to do I actually have in non sport mode in my 430D?

So I guess the power is pretty much enough, but I really would miss 4WD :/
But I also hate the weight of the M50 (eben the 40) its just way to heavy...
I dont now...

 

But I also hate the weight of the M50 (eben the 40) its just way to heavy...

What about the weight do you see as the issue?

 

Well, Im anot sure but there was not one reviewer wich not sayed that it feels in any way heavy. I probably saw 90% of all reviews in German and english and even some in other lagugagues with subtitle.
And again since I can allready feel 25% fuel agianst 100% wich is like 40kg, the 500kg difference for allmost the same size must be a huge difference dosent matter which supensions or wheels.
Its just a huge mass difference which goes into the kurve.