originally can not beat BT...BT much more better...
1) wiring harness with BT ECU
2) Air temp sensor
3) BT air filter hose
4) Map sensor
5) if using AFR, need to reroute the vacuum hose for better AFR meter reading, no flucking reading...Please refer to this : 4A-GE 20V Enthusiast :: [DIY] - Vacuum line :: August :: 2007
price...normally RM1500...that was 3 years ago...now days...don't know
Mostly,changing wiring wont do anything (if both of the wiring is in good condition lah),it's the 'brain' that makes the difference.Wiring is just a medium to transfer electricity.