560 SEL No Start

[standard125r]

My SEL has had a hard start situation for a few months. It always starts, but I have to crank on it for a minute (seems alot longer) when it did start it would idle very rough, and any added gas would cause the car to die. Once it warmed up things were fine. The guy I bought the car from said that he had some adjust the car so it would start. Anyhow, I went to the dealership and the tech said to run some techron through the motor, which I did. It helped at first, but then the problem got worse. I spoke w/the tech again, and he suggested the control head was probably varnished up. So I purchased a new one and installed it. Now the car will not start at all. When I push down on the sensor plate w/ the oumps running there is a screaming sound from the injectors. I know the question will be did you mess w/the mixture screw. I DID NOT. I can hear fuel or air at the injector head. Any suggestions?