Yes the weber IAW ecu's are old but a more modern ecu does'nt help with bosch 403's. They have a very shallow angle pencil spray pattern, which means the atomisation of the fuel is very poor.

If you monitor HC levels at idle when using 403's they are lowest when running the engine slightly richer. (i.e. around 12.5:1) It's quite evident in the engine tone too, with a noticably lumpy sounding idle as you lean the idle off towards 14.7:1.

This issue is not evident at all with Siemens 3102 injectors which have the same flow rate as 403's.