Chevrolet Repair: Suburban 99 6.5 Diesel - hesitation, 2007 chevy trucks, size trucks

Question
I Have a 99 suburban, with 85K Km, I change the PMD, the fuel pump, and the
gas pedal. I steel have an intermitent problem with the accelerator, when i'm
driving in a bumpy road, push teh break or make a violent turn, when i step
in teh gas pedal nothing happenes, i fully realese the pedal and step againt
and the truck reacts.
I also noticed that when i drive in the road at 2000 RMP i get only about 120
KM/h, my older suburban (94) give me more end sepped than this one.
Can both problems be related?
As soon as i get in the road with the Cruise control no problem or hesitation,
only at low speed or when start to move. Sometimes i can step fully in the
pedal and the truck do not react until i realease and push it back again
In  my country ther are very few people who knos about amricna cars an no
one can solve the problem.
Can a computer flush and reload help ?
I will apprecieate any help
Thanks

Answer
Hello Oscar,
I would like for you to follow the link I leave here, and sign into Chevytalk. I am Fixitfox33 there, so that is what the referral link is from.
Then go to the full size trucks and Suburbans, and post that same question.
I am only one person, but there, hundreds of people will read the question, and you will get some suggestions.
It is totally free. I will look for you there.

http://www.chevytalk.org/fusionbb/index.php?referral/23610/

Then this is the 99 Truck link.
http://www.chevytalk.org/fusionbb/showforum.php?fid/34/keyword/1999-2007_Chevy_T...

And this is a link with your question asked, so check it out.
http://www.chevytalk.org/fusionbb/showtopic.php?fid/34/tid/164008/pid/1202419/po...

You will love that site.
Van