Hi i have a 1989 180sx had a ca18det , now i have put in a sr20det black top , i have recently got it registered and taken it for test drive it hesitates when you hit around 4000 rpm and if i put my foot down more to the floor it hesitates more and sometimes it back fires and black smoke comes out .I have changed the spark plugs and gaped them to 0.8mm . when it starts to hesitate it shows on my auto meter gauge its lean . also it has the standard exhaust from the ca18det and the co2 sensor near the catalitic converter is not hooked up someone told me that the sr20det does not use it, the engine is stock the only thing it has is a front mount intercooler and air filter , ill also add i changed all the wiring including dash wiring because i transfered it from the half cut. if i drive the car and not put my foot down more than half way it runs ok but when i put it down past half it hesitates and backfires out of exhaust really loud like gun shot. i really need help to fix this problem any one out ? would be great