ITRCA

Ok car runs of from idle to 3900 but as soon as it hits 4 it takes off alot better. Sometimes the car will even spit and sputter till it hits 4 then it runs perfect.You can feel it pull alot harder once it hits 4 grand weather im on the gas or barly on the gas, i originally thought it could be the adjustable cam gears and figured the timing was set this way but i dont no any ideas?

TPS or VSS, check the connections for moisture or rot. then see if they are getting the right signals. you will need the service manual or someone kind enough to post it for you.
Also, have you checked the distributer, it could have taken a dump.

Any CEL's associated with it?

Any other maintenance or recently installed parts?