my ls 400 runs fine as long as i dont try and hit the gas pedal to fast accelarat at any speed it jerks and i have to let up off the gas and let it take its own time to pick up speed!!!

 

You could have a really bad intake leak or vacuum leak. On most other cars the first thing you'd look at would be the fuel filter or the air filter and look for restriction but in this case I'll guess that you have a cracked air intake hose.
Test it out by spraying starter fluid all over the intake pipes and seeing if the revs increase

 

try the MAS and get some mas cleaner and just give is a spray some time that helps!!!

 

Will it rev freely in neutral? If not, it could be a plugged cat.

 

its prolly the ecu, same issue ive been dealing with for 2 months.