you need the short rear shock tower and medium shocks and springs, the threaded shocks aren't really an upgrade as they are not velvet coated, the rear aluminum uprights, rear aluminum toe block (that most of us bought, any way), radio tray and wing aluminum mounts and a longer king pin??????, new body and air filter. But you are losing on all the original TKI hard coated pieces, so if you have an original TKI and upgrade to TKI2, you have a much better "SPEC" car, and lighter. My original TKI upgraded to TKI2 with JR 9100s and T, OS speed with 2050 mp pipe, 2700 nimh pack, airtronics m11x, ready to race with transponder and body, no rims/tires or fuel weights in at 2999 grams. My SE weights in at 3208 with the exact same equipment.