Hi.
To get the same good feeling with the TKI4 as the TKI3 you need the TKI3 B-plate and 1,3x8 white pistons in the shocks. The B-plate is what makes the BIG differnece in theese two cars. I have not had the TKI2 so i don`t rember what rear hubs were on that car.
Put the TKI3 B-plate on and change the droop settings and the car is awesome! the diffoils you have put in makes the car worse. Use 5-5-3=easy to drive.
If you do not get more than 8:30 with the OS B2101 (if thats what you have) you are either HEAVY on your throttle or your engines is tuned wrong. I run on big tracks here in Norway and gets easely 10. Only car i know thats a fuelhog is the MBX6 and 7. The best car for fuel economy is the Losi 8ight, but thats the only thing good with that car, LOL :-)