oonbc,
You quote:
"can someone educate me abit about MAP or MAF sensor for a piggy back? and what is the difference a piggy back with or without it? is it essential?"
Well, the MAP or MAF sensor for a piggy back is to re-calibrate the output signal,like fuel map, rpm X load ( map or maf )
Example, a 1600cc engine, you re-bore to 1800 cc. Since engine cc increase, you alos have to upgrade your injectors, say from 210cc to 285cc.
Now, when you want to idle the engine, the A/F show very rich. What you can do is, you have to reduce the MAP or MAF signal from the input table according to rpm and loading.
That mean MAP or MAF will reduce the signal and feel to the stock ecu, then, the stock ecu will re-calcualate the volume of the fuel in order you have smooth idle.
If you re-gain the output signal from the input table, you will have bad idle for your engine.
For cheap side, you can re-chip or burn the eprom after mod the fuel and ign table like Honda VTEC, software editor like CROME.
Goodd Luck.