The GQ ECU merely doesn't actuate the pump for the 5th injector. So, while it effectively is disabled with that ECU it still monitors for the pump itself as well as the catalyst temperature sensors. You will have to leave them installed or wire in resistors to fool it into thinking they're still installed. I used a couple 220 ohm resistors to emulate the temp sensors.
OR, you can swap to the FA ECU from the 97 Passat that doesn't monitor for any of that, BUT, the problem there is you would have to rewire the glow plug system. The FA ECU has diagnostics for the glow plugs and uses a completely different relay to accomplish it, located in a different slot with different wiring. The GQ and BK ECUs use a dummy on off relay, no diagnostics, so they don't know if you have a bad glow plug or not...