FSD/PMD variations 6.5 diesel

[MrTrot]

Help...

I have 1998 Suburban 2500 4x4 diesel 6.5 turbo.

Was having performance issues stalling etc., read about FSD/PMD failures and

took it to GM dealer. He said codes indicated I needed new main pump @2,000.

I asked him to just change the FSD/PMD first, and he reluctantly did and it cured

the problem. Less than 3 months later it started dying again so I took it back in

and convinced him to change out the FSD under warranty, which he did. Here is

my dilema: Now that the new FSD has been installed the dying engine has again

be resolved. However, I swear the engine now has a different "feel" particularly

when has the least load. I would best desribe it as a very mild pulsing that you can

feel in the accelerator pedal but don't see on the tach. Almost like the old big block

gas engines when the timing was just a little too far advanced. It just doesn't feel

right. Well the dealer admitted that even if he drove it he would not notice it and

the codes would not show anything. Sorry for the wordiness, but I have a couple

of questions. 1. Is it just me or is this a defective replacement FSD/PMD? and

2. I overheard one of the mechanics saying that these units have a resistor on them

that GM keeps changing, or even eliminating. What is the scoop on this? Shouldn't

the new replacement part be GM's latest and greatest? Thanks for listening and

helping out this newbie...