kx450kid

hi i just did a motor swap into my 98 honda civic hatchback it is a b18b1 ls motor the car was turbo charged before the swap it is not now but after putting it in and wired up with a stock ecu it starts up fine and runs fine when cold but when it warms up it just will not seem to let me give it any gas and wants to die unless i push the clutch in. i am completely lost on what to do next i have checked the wiring over and over and i have one 02 sensor hooked up due to i only have a header pipe on because i have to get the rest of the exhaust on any thoughts on what i could do to get it running normal?