Alright so I was right kinda, theres a dummy plug that I thought was for the intake air temp sensor, right where you where talking about. But there might be a sensor still there, since we are using a the old 260E air box and this 300E is a 89. So there could be two wires laying somewhere in the engine bay but I didnt really find any. Oh and about those sensors on the head so these cars have one pole going places instead of a +/- i am use to my 86-87 bmws but its all still bosch just alot of differences. Alright well I will see if this car still has a iat sensor wire laying around. Anyone have a pic of the engine bay of a 300E since I am a little confused as for the vacumm lines, the 260E is the same but it seems different or this 300 has been tampered with a little. FPR line I need to see where that line goes and the front sensor on the head has two vacumm lines and I know one goes to the wheel well and the other I have no clue but then again this could be cause we are using the 260E intake air box. Also no advice on the backfire/hesitation from standstill. Also anyone know what the idle is suppose to be set at on the 300E. Also there is a switch on the throttle not tps is like a micro switch is that switch suppose to be pressed in at idle? oh thanks augapfel for the info so far, hey I am from pa also LOL.