Start with fuel filter. Was an upgraded converter installed? Did the problem just occur all at once or has it been slowly getting worse? Was it dirrectly after the transmission work? Any codes on the truck?

Tuning of the pump isnt recomended until previous problems have been dealt with UNLESS it is a pump related issue.

It could be anything, Turbo , Injection timing slipped, Transmission problems....the list is endless!

 

i can get 70mph in about 300 feet,that does not sound right at all!

 

I guess your truck is bad *** then

my Mitsubishi Fuso FE Cabover truck with 135 hp 4 banger does 60 in about 10 seconds so I am sure you have a fuel problem

 

i can go 0-86mph in 8.68 secs