1977 450sel

I purchased this car in November, and from the beginning it was a rough cold start. But after it had warmed up it would start fine. However, the problem has gotten worse the temperature doesn't seem to make a difference in the starting. Also it has now started to idle roughly at stops, the rpm's drop as does the oil pressure. The car doesn't die at stops but I think it is leading to that. I have started to check into the fuel injection system. K-Jetronic. I was wondering if anyone had some input as to the problem area or general knowledge of this system. Thanks. P.S. this is my first car and I love it!