Problems with new 4045sfm85

[Finagler]

I had a new 4045sfm85 M5 315 HP installed in my 36' single engine Grand Banks Trawler. This engine has knocked like pre-ignition and put out white smoke in the rpm range 1400 to 1600 since new. Accelerating through this range it puts out a puff of smoke and rattles. Trying to cruise it this range it knocks and smokes. Higher and lower RPM it runs fine. The dealer who installed it has tried everything we could think of to fix it. Turbocharger and waste gate changed, computer changed, propeller changed, new muffler to eliminate back pressure, injectors changed and flushed, fuel replaced after tanks cleaned, and engine run off a separate battery to eliminate electric interference. All this has taken 18 months and Nothing fixes the problem. Deere Corporate has not been responsive in suggesting a fix, leaving it to the dealer and Distributor in the PNW. If anyone has a suggestion how to fix it or can give me a contact in Deere Corporate who might own the problem I would really appreciate it!