stalling 944, reference sensor wire?

[rudidelange]

A *** mechanic cut into one of reference sensor wires at the firewall (harness) before I bought the car. Noticing the taped wiring I undid the tape and soldered new female plugs on the three wires coming from the harness. One was a coax cable. I extended the wires with some elctrical wiring from an auto electrician's shop. The vehicle refused to start, so I checked my poor soldering techniques and found one wore loose. I now crimped them on - and it started with the first crank. I also checked the DME relay - thats ok. The cars runs fine, and on three occasions it jerked - like a misfire and today stalled in rush hour traffic. I open the hood and pressed the "fixed" wires with my hand, it started first time.
My question: Is this wher the problem lies? I read in previous discussions that a new wiring harness is recommended because the coax cable prevents coil interference and that extending the wires area no no.?

[SoCal Driver]

Best to find another car that has the complete uncut sensor wire(s) and use then on your car. Try BMW's and others that use these types of sensors. As you have found out it's near impossible to fix these.