[HDi fun]

It's not the torque output that loads up the camshaft belt. It does not form part of the drive train.

It's the load that the PD injectors put upon it, being directly driven by the camshaft.

My 406 had a twin cam engine, delivered 235lbft in stock tune and over 320lbft with a remap but the cambelt change interval on that was every 96,000 miles. That had a cambelt driven high pressure fuel pump but it only presented a constant load, not the twice per revolution torque reversal that the PDs presented.