I generally agree to the statement that the D-Jetronic is not suitable for a modified engine. This is due to the fact that the system is based on the manifold vacuum (thus D for 'Druck'). The vacuum is affected by porting, larger valves, engine displacement and cam profiles. It is nearly impossible to re-adjust the pressure sensor, so only minor modifications can be compensated by changing parameters like fuel delivery pressure.

The K-Jetronic offers more options for the amateur to change settings. Literature is available on the subject.

However I am still using the orginal D-Jetronic on my sligthly modified engine (larger valves, re-profiled cam, etc.) with good results.

There is another alternative to the DCOE Webers:

Lumenition and others offer throttle bodies for use with fuel injection systems. These throttle bodies fit any DCOE manifold, thus can be used on many Volvo engines. Full user-programmable injection systems like the Weber Alpha and others can be used replace the former BOSCH hardware. In theory this would be the optimal system, offering four throttles bodies and straigth ports for maximum performance. However I've not seen or driven such an engine yet. Maybe it's just too expensive...