He scratch built almost all the finer details inside and out to make the model as realistic as possible. The N2 kit was all hand sculpted from putty (actually Aoshima now makes an N2 kit!)
Anyone thats built the Fujimi AE86 will know how basic it is and there are a number of flaws in it. The Aoshima versions are slightly better and more realistic and some include a 4AGE but that doesn't stop him from modifying and "tuning" it!