6nz jake sticking?

Have a 475 6nz in a freightliner that I bought a few weeks ago. Truck ran good since we bought. It broke the rocker bolts on 3 or 4 and it messed up the the jake brake. We were in a pinch and needed the truck so we put used parts in it and it had a different part # on the jake. The driver in the truck says the it does not have the "recovery" it used to pull hills (100,000 lb + loads) . My question is that could the jake with the different part # be sticking ? My other thought it the the broken rocker bolts might of messed up an injector. Any input is appreciated.