Guess what happened, I found out the Fuse "F1" on one of the computer modules in the computer box was burnt.
Replacing it with a 10 Amp solved Cruise control problems, besides that it fixed my ABS problem, and also my engine rpm can reach 6000 if I kickdown, before it bogged down as soon as it reached 5000.
I just got the service CD yesterday, from the schematic, it seems that 10 A fuse "F1" is used to protect the ABS circuit and Cruise control/Accelerator.
Today I had to handover this 400E to my wife, I bought this car for her, after I fixed these three problems by just replacing a fuse, I no longer have excuses for not letting her to drive it, since it has become a perfect car.
After I drove my sluggish Explorer to work, I decided I will buy another old Mercedes for myself.
99 BMW 540i 6-speed 110K Km
03 SAAB 9-5 wagon 80K Km
92 400E (Sold) 245K km
Still missing the days with the Benz, it kept me busy.