i got a 3in lift said i was not going to any higher then got out playing and i want more flex so i need to get up another 1.5 to get rc long arm kit. but at what point do i need to adjust my pinon angle.

i play with fast cars not 4x4 so im in the bark on this one.

 

Your front pinion angle will get adjusted and set when you install the long arms. You will probably need to shim the back with 4.5 inches of lift.