1. d4 nf6 2. e3?!

 seen this happen in  couple of games... do you guys prefer 

g6, e6, d5, or even c5?

There is also b6. 

White seems to be heading for a Colle System, so I would prefer 2. ... g6.

Why are you suggesting that 2.e3 is a dubious move? It seems perfectly reasonable and can lead into some English variations, some Queen's Gambit variations, the Nimzo-Larsen, or other openings as well as possibly being independent

My guess would be that white's opting for a Stonewall or a colle as blueemu mentioned. nothing a KID can't handle! (why not?)

well from various opening databases it appears white scores significantly less than black---- by the 2nd move!

Sure, but the transpositions lead to positions where White scores quite well...

solid for me is 2.e6 then 3.Be7 or imediate d5 then c5 to follow. 

I actually misread the moves, 2.e3 is typical of a Colle setup with Bd3 and is certainly not dubious. I thought you were talking about 1.Nf3 and 2.e3 which could lead to the openings I listed. Black cannot hope to get an advantage out of a major opening unless White screws up, and 2.e3 is not a screw-up.

In my rating range (  quite low ) , this is the second-most often played variant by my  opponents , after 2.c4 . So for the sake of my own handwritten lists I was looking for a name , but could´t find any , even on numerous famous chess sites .

But maybe someone has already given a suggestion in a book , like " White Stonewall Preparation " , " Colle vs Indian " etc ... ?

My main response has been 2...d5 , where my opponents go often into an almost Colle set-up . In the future I plan maybe to try 2...c5 and see what happens .

always the same story...

Depends on what u play on "big lines".

Giving advice with KI set up, Grunfeld set up, etc... is a bit useless if u play Nimzo indian...

I quite like this approach:

no because de colle system need you move d5 for her ambitions power so you can do c5

I dont use this opening a lot

It's good that you don't use it a lot. You have just blundered away your knight on move 3.

I play 1.d4 2.e3 and Nf3... after discovering David Rudel's work on 9.b4!? Colle Koltanowski against Black's Nc6 line (playing a true Semi-Slav as White with a move, also got a seal of approval from Milos Pavlovic)

That stated ... I play the Semi-Classical var against the KID. (at my level i.e. 1800+ Lichess) the KID doesn't present as many challenges as the Nc6 main line of the Colle Koltanowski.

I have three lines

8.b4 & 9.Bb2

6.b3 & 7.Bb2

and 8. dxe5 w/ a delayed e4

At my level.... I catch more than a few KID players off guard playing the Semi-Classical. There is not a lot of theory on it published, and seems to be ignored by most KID theorist.