I have a 92 300D 2.5 with the pressure wastegate conversion. Awesome conversion and should be done on every 300D 2.5 imo!

Your pressures seem just slightly high. The Mercedes spec is 12 psi max. I get about 2 psi less across the same rpm's you listed. The turbo is all-in by about 2500 rpm anyway, so 14 psi should be about your max even at higher rpm. 14 vs 12 shouldn't cause any harm. I have heard of pressures as high as 20 without damage, but don't want to say for sure 20 is ok. But I would think that 14 is probably ok. Enjoy that 300D 2.5, one of the best cars ever made by MB!

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1972 280SE 4.5
1984 300SD, 250K
1991 300SE, 89K
1992 300D (330K miles when KIA'd by mother-in-law 8/10/09 - still sitting in my barn)
1994 E320, 109K
1995 E420, 60K
Proud Member of the Mercedes Benz Club of America - Idaho Chapter