Well, let me say first off that I am new to this forum. I have already learned a LOT from reading the posts here and I enjoy looking at everyone's beautiful rides!!!

I have been having a continual problem with my 87 300E which I will explain. First, here is some backround information. I purchased the car in May 2007. It supposedly wouldn't start if it had rained. I figured cap, rotor. So I bought it and started to drive it. Well after about an hour of driving and sitting at a light, it would just die........... After a few minutes (10 or so) it would start and be on its way. I figured something was gettiing hot and breaking down, fuel pump? maybe the cap & rotor? Possibly the fuel distributer getting a vapor lock? So I started to change and upgrade some things. I installed a new cap, rotor, wires, plugs, coil, supressor housing and cover. I removed the old air box and installed a cold air intake. I did this to uncover the fuel distributer and allow air to flow over it better, for heat dissipation. So I fire her up and drive around, man it runs absolutely great!!! I haven't gone an hour yet though. I tool over to a buddy's house a week later and park, come out 15 minutes later and no start!!!!
Dangit! I unplug some things and viola! it starts. I now figure the ECU is heating up and killing the spark as I can hear the fuel pump cycle. I pick up a used (tested) ECU from Ebay and install it. I drive around the block, aboout five miles and it's purring like a kitten!!! I pull into my driveway and let it idle for a bit. Then it starts to miss a little, and now it is hunting for an idle speed, running @ 1000 rpm, surges a bit to 1200, drops to 500, suddenly surges to 1200 again, continually running rougher then it just drops dead!!!!
I have checked the O2 sensor, checked grounds, I just don't know where to go from here. I have been reading about the overload relay, but it seems that was changed recently. Any help where to go or something to check that I may be ovelooking would really be appreciated!

The car has 194K on it, 3.0 litre.
Thanks in advance!

Sam