Why would my car do this?

[oilslick]

Hello All,

I just recently got the 300D engine installed into my w123 and for the last two days it ran super great! NOW it won't pull the teeth out of your mouth. When I depress the fuel pedal it takes it a while to increase speed at idle and under load. I can floor the pedal and the engine will slowly increase in rpms.

Here's a thought. I did put fuel in the tank the night before this problem made itself manifest. I bought fuel from a station that had been closed down for almost a year. I know that anything is possible but how likely is it that the fuel tanks at the station have water in them or algae? Would water or algae cause this kind of problem? The engine accelerates smoothly but slowly. Before this occurred the car was cruising beautifully at speeds well over 70 mph. I drive it the next morning and it won't go "fer nuthin'". Briefly yesterday morning it seemed to "break loose" but after I shut it off for a few hours and then restarted it to drive it it went right back to slowly increasing rpms and moving ever so slowly.

No smoke except at start-up. No water in oil and no oil in water. Normal temperature. Tank gauge is now at the first line headed toward empty.

Kevin