Hey HondaSwap, I recently put an OBD2b USDM H22A4 in my '00 EK, running on a stock OBD1 JDM P13 ecu. I used to have a boosted D in my car and can usually trouble shoot issues concerning Air/Fuel ratios, but searching has shown me there seems to be a lot of people that have no idea what they're talking about, providing solutions that don't work to fix the "H22 hesitation issue", so I intend to make a thread that will be informative and actual help solve this issue. The Problem My H22 seems to run rich - I can tell by the way it pops and backfires when I downshift. It also hesitates and revs slowly when accelerating, smells like unburned fuel, and when VTEC engages it more or less falls on it's face for about 1/2 a second before sluggishly accelerating again. The tricky part is it seems to be temperature related because when I first start the car in the morning; the throttle response is quick and snappy, the car accelerates really well, and it doesn't pop and backfire when I down shift. This only lasts for about 20 minutes until the car is warmed up to normal operating temperature. Checking CEL codes shows: Code 10 (Intake Air Temperature Sensor) - Due to it not being connected. Code 12 (EGR) - Also not connected (I explain why below) Code 20 (Electrical Load Detector) - My Civic is from Canada where EKs don't have an ELD in the fuse panel. What my research has found EGR - It seems to be 50/50 whether or not the EGR system actually has any affect on engine performance. Anybody that posts saying that it does affect performance doesn't own an H22, and anyone that does own an H22 and has it blocked off says they notice no difference; so I'm willing to rule out EGR. O2 Sensor - A lot of people seem to say it could potentially be the O2 sensor, but considering my ECU isn't throwing any codes for O2, I kind of dropped that on the priority list as well. Knock Sensor - Knock sensor was the cause of the problem for people that had the Knock sensor CEL code (code 23), but my ECU isn't throwing this code. I replaced my Knock Sensor for good measure, but still noticed no difference in engine performance. Ignition Timing - Some people say the OBD1 P13 will retard ignition timing if the Knock Sensor, EGR, or O2 sensor are bad but I haven't been able to find anyone confirming this. I think my next step will be to advance my ignition timing and double check it with a timing light to make sure it's right, but my issue is associated with temperature so it gives me doubts that my timing is off. Summary - My Knock sensor is brand new - My EGR valve is disconnected - I don't have any O2 sensor codes - My car works great when cold, and shitty when warmed up My questions - What could be the cause of this problem? - Has anyone actually noticed a difference with the EGR connected/disconnect, blocked/unblocked? - Is there any other options I've missed? I apologize for the long post, but I've done some extensive research and only seem to turn up bullshit answers. Help is appreciated!