we took our 1995 r model mack and swapped out the 400 motor and droped in a used 427, about three years ago. after some computer issues we finnally got the truck on the road, the 427 was incredably strong, right up till 3 weeks ago. the motor started to hitch and hesitate on hills, so we took it to a mack shop, the mechanic changed the injection pump with a good working used one and sent us on our way. the truck didnt hesitate any more, but lacked power, so he told us to take the original pump to get calibrated. we had the original looked at and calibrated, but there was nothing wrong with the pump, it was working fine, besides a little timing and cleaning. so we put it back on the truck, still lacking power. so they said it wasnt the pump it was the wiring harness to the pump, they changed it with a new one and gave us the truck back. we took the truck on the road with a EMPTY log trailer behind and it didnt just lack power now it could barely haul itself. we had to drop the trailer and take the truck to another mack shop. that shop said our turbo was cracked, so we put a good working used one on and still nothing, changed the air filter and fuel filters and all of the fuel lines, still nothing. new air to air, 6 new injectors, new intake sensors, boost gauge, STILL NO POWER. we can only get 15 to 20 psi boost from the turbo, 2 mechanics say the fuel pressure is fine 1 says it fluctuates. the temp gauge will read 180 after a quick run but the comp hooked up will read 108 and a temp gun shot at the manifold will read 103. first thing tommorrow morning i want to check all connections on the new wiring harness because after it was installed we lost all power. oh and the vavles have been set as well. if anyone has ideas or input please help. thanks frustrated 427. p.s. the turbo for the 427 is actually off of a 400 because the 427 turbo will not fit with the hood closed but the motor had tremendice power before with the other 400 turbo.