ZR-6 Knock Sensor issue

Hi all,

Been reading up on the issue we experience, but many issues regarding the knock sensor are due to winterizing activities not replacing the knock sensor or proper connecitons.

In our case the issue is a bit different.

We own a 2006 210 SANTE with ZR6, the knock sensors (2 sensors) are located underneath the intake manifold.

We use the boat in the Netherlands, running on 95 octane unleaded fuel.

The issue we experience is when pulling a wakeboarder revving up even under 3000 rpm the tach display starts beeping and showing "knock sensor see dealer".
When we place the RINDA CodeMate on the engine it throws a code 44 (Knock Sensor 1 or 2 Inactive).
Resetting the ECM helps for about 10 mins or so, and again the ECM throws code 44.

Testing the resistance from ECM Terminals J1-1 and J1-17 return 99 kOhm, well whithin range what the MEFI-4 diagnostics manual tells us.

Last week we replaced both the knock sensors, noticed that the old ones were torques to over 50 Nm, the new ones we torques to specs (20 Nm).
No teflon tape, thread bond or anything used, cleaned out the tread and seat of the sensors in the engine block before installing.

Today we took her out for a session of wakeboarding, unfortunately after about 15 minutes the errors started showing up again.

My question is if someone else around here has experienced the same issues?

The last resort in the MEFI-4 diagnostics manual sais replacing the ECM....

Any information appreciated.

Thanks.

Marc.