With Regina engines, the CPS does not connect to the power stage, it connects to the Rex i ignition controller, which then passes the signal on to the fuel ECU. The ignition controller has a control line to the combined power stage relay and coil to call for spark and adjust the timing advance.

Are you looking at a Renix system? It does have the CPS going to the combined power stage and coil, with no ignition controller and presumably only used on carb'd engines. Maybe check my reply just now to Bill elsewhere here in case I'm missing something in your symptoms or diagnostic testing you've done. I'm very much thinking fuel side at the moment.

The Hayne's wiring diagrams can be difficult to use. Most other manuals only have schematics, good for basic connections, but not so much for years, engine versions and detailed testing. Better for you to find a Volvo green manual online for a year close to yours, either 740 or 940. You're near the end of the 740 models (and possibily a non-North American market car?) and now more divergent from the end of the 240 series and the beginning of the 940 series than many are familiar with here, so things maybe a bit different from what some of us like me are familiar with.
--
Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now