what exhaust manifold do u have? obd0 b16's have a weird dual o2 sensor arrangment which can cause trouble if u have an aftermarket header that doesnt do this. The LS map may be a bitch richer. THe b16 compensates by lower base FP but i beleive the ls will still be a tad richer. but nothing enuf to be a night and day different liek you are descring. Has nothing todo with vtec wiring.