So, my buddy managed to solve the problem! This Transistor was damaged:

 

 

It's original a NPN transistor, type NEC 2SC2719, and this type isn't in production any more since several years. But you can just use a more common type with the same or better technical datas, so my buddy choosed a BD139 as replacement.

 

This is a very standard type and available from nearly every semiconductor company, for example Texas Instruments, STM, Motorola/Freescale, Fairchild, Siemens, Philips and so on. Here are a few datasheets for BD139: http://www.alldatasheet.com/view.jsp?Searchword=BD139

Anf here is a document which describes the original one: http://www.datasheetarchive.com/datasheet.php?article=3746501

 

As you can see, the BD139 is far better, but because it's such a common part, it's really cheap. One piece cost about 0.50 US$ here in Germany. The replacement is easy, you can do it with basic soldering knowledge.

 

So, the ECU now works fine as it should! I write an article for the USRM in within the next hours!

 

AND: My problems regarding acceleration are gone!! So it seems that the ECUs interchangeable to some degree and the engine should run, but it runs bad. The test drive was a real pleasure

Thanks for the update. That is the same exact thing that happened to mine though I had a different model ECU. Glad you got it corrected. This will help some others that have the same problem.

 

Can you tell us what the Q number is of the transistor? You can't see what the number is in the pictures.

Of course: It's Q701! I forgot to mention it...

 

I made the article: http://www.ultimatesubaru.org/forum/showthread.php?t=76906

 

I hope this will help other people, too

that is awesome! thanks for posting all of that information. based on the all that i've read and we've talked off-line i can almost gaurantee this is my issue as well with mine. thanks! that is a fantastic write up! i'm an electronic idiot and it all made perfect sense! thanks again.

Sweet man! This is a hugely valuable addition to the USRM

Do you have a pic of where that transistor is located? I'm having the same problem with my ECM.

Just follow the link to the USRM (http://www.ultimatesubaru.org/forum/showthread.php?t=76906) and download the attached file "ECU_repair.zip". Extract that ZIP file and you'll find a PNG picture wichich shows Q701!

 

The number is printed on the circuit board, so you should find it.