2 months ago i swapped my vx.
stuck with the single cam harness.
changed out the fuel injectors and all the needed sensors, basically converted odb2 motor to obd1. a buddy a mine let me borrow hit odb1 dizzy and i don't know how old or or in what shape its in.

i ran my vx ecu for the first 2 weeks and vtec would hit at 3k so i would drive without the vtec solenoid plugged in.
towards the end of those 2 weeks with the vx ecu my car would sputtering on take off and lag until i hit 4,000 RPM.

i changed the ecu out, and replaced the sparkplugs. the car was perfect until
2 weeks ago.

now the problem is at low rpm the car lags until it crosses 4,000 rpm. and my vtec hits at 5. so it basically feels like a double vtec.

when i start the car and rev in neutral it backfires.
------------------
b16a2
short ram intake
and p28 ecu
straight piped.
car starts right up

 

get your p28 chipped for a b16a or pick up a p30

sounds like you are using a stock p28

 

but why does it lag and do the sputtering sometimes and run right other times

 

probably due to the signal that the ecu send to the fuel injectors causing a misfire or the car running too lean. hense more speed= more fuel

 

Any check engine lights?
What injectors did you use?
What distributor did you use?
Did you check ignition timing?