hey guys, need to pick some brainz....

I’ve got a 99 dx hatch with a B16a, running an EM1 harness and ecu.

No dtc, but I’ve felt like the car was feeling slightly under powered in certain situations, I.e. under heavy acceleration in third or fourth. Almost that ‘barely perceptible lean’ misfire that only people like us would notice but not like a full on ‘dead cylinder’ miss that is very noticeable.

Hooked up a scan tool:

everything looks normal during idle, LTFT is at like -3 to -1, not bad for a high mileage engine.

HOWEVER! Under acceleration, especially above 3500 rpm, stft drops to between -15 and -30. It’s trying to compensate for a supposedly rich condition and leaning way out.

is this normal?

what could be going on here? What are good things to check?

Bad o2 sensor

Always possible, though it did seem to be behaving on the live data on my scan tool.

its a cheap Bosch number, should I get a denso brand?

I’ve got a fuel pump I took out of my em1 parts car. Runs about 28-30psi at idle