the title is the question!

emissions system on the S, less HP as well

As Joey said, S engine has EGR, and I believe that they all have a MAF sensor as well.

LD has an EGR and two more solenoids, perhaps a MAF instead of a MAP as well as 9.25" sf rear or smaller.

F engines mean HD, 10.5" FF axles usually.

now that makes alot of sence reading this post, and from old posts of close topic.

thanks for the info guys!

Is there a power difference? My F truck feels a lot more powerful than my friends K2500. Not sure what he has but maybe this is the reason.

He probably has 3.73 gears compared to your 4.10s. The lower gears will make it feel alot more powerful.

Chad