Are we talking the OM 617.912/3 engines? if so, the compression is not the problem. The strength of the piston is-- The gudgeon (wrist) pin is somewhat larger on the Turbo version. The compression Ratio is .5 points higher (22:1 as apposed to 21.5:1 non turbo) for a turbo piston to compensate for the greater valve overlap of the turbo camshaft. If I had a turbo, Id give it a go on mine, I have never heared of a piston breaking up on an OM 617! But I would recommend fitting an Intercooler at the same time to reduce thermal stresses, especially if you like to use the extra performance!, Get one off a scrap Jap 4x4 Toyota or Isuzu with a 3 L engine, they are usually quite a good one. Dont forget you have to change the fuel pump too!