i have an ek hatch wit a b16a when i bought the car vtec was not hooked up and it had an ls none vtec ecu. i just wired up vtec and put an obd2 gsr p72 ecu and it works but runs shitty it boges alittle before hittin vtec and the tach rpms goes up and down... any ideassss???? plz help

 

well you will have a code for the intake butterflys . if it's a jdm motor it won't have a crank flux sensor ( only north american ecu's look for it ) if its a jdm ecu it could be from an automatic could be lots of things try bieng more specific like when do the rpms go up and down at idle or just when its in vtec ?

 

like usaually around 4-5k it starts to go up and down