More Stumbling issues please help!!!

[radlark]

Hello all I am writing this post with a heavy heart! I have done the search and have read the post, I have developed a stumbling problem and it is intermittent! I have read all the possible causes but they only apply to newer MBZ, I have an 87 420 SEL and I would like to know the following:

1. Where would the ICM be located on my car?
2. Where would I look for the TPS (throttle position sensor)
3. Is there a way to run a diagnostics on this car?
4. I have heard of people making there own "scan tool" is that possible with this year of a vehicle
5. I have just changed the spark plugs and used Denso plugs (non-platinum)
6. It doesn't shut off it just stumbles a little I checked for vacuum leaks and all is good, what else?
7. Where is the Egr located?
8. Is there a manual that can be purchased for this car?

I realize this has been posted but I have done the search and to no avail it only applies to the newer models this is my first Benz (boy these parts are expensive BTW) and I really love the car, any and all suggestions are welcomed.
I REALLY appreciate all responses as I am new to the board.

[csnow]

Under what conditions does it stumble?

[maheath]

This book goes into more detail about the fuel injection system than anything else I've seen.

http://www.amazon.com/exec/obidos/tg/detail/-/0837603005

The only place I know of to get the official service CD are the illegal copies sold on eBay. The 126 chassis is a 2-CD set.

[radlark]

The car stumbles when at a stop light and when you take off it stumbles and if I am at the light and about to merge on to the freeway it seems as though it is missing until about 75 mph and then after about 30 seconds it smooths out it is intermittent and I have utilized the search threads and have tried the obvious solutions but to no avail. PLEASE HELP!!