cooper1340s

I have a JDM D15B vtec engine installed in a classic mini cooper. Engine is stock except for Hondata s300 chipped ECU and dyno tuning.Engine starts fine and runs well until it reaches operating temperature and then chokes when throttle is aplied normally. In or der for car to move, have to apply throttle very delicately and then car will slowly accelerate. Push throttle too hard and engine will bog down. Every once in a while engine will break up badly and has to be shut off for a couple of minutes and then it will start again and run with throttle applied very delicately. Engine has new PGM-FI relay, new distributor, new map sensor, new fuel pump and filter, new hot idle motor, new spark plugs and new fuel pressure regulator. Any ideas?