Well it sounds like a afm flap issue to me personally. In open loop it's running strictly off of the afm until the o2 warms up enough to work. Also check all your vacuum hoses.If I had more information on which sensors the ECU is evaluating to determine when to trigger the FPR I could narrow down my search for the delayed acceleration issue. But this is all the FSM gives me
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Both banks tie in after the cats, I mean I can scope the O2 sensors and determine the A/F Ratio based on voltage seen, since Lambda is 450mv which = 14.7:1 A/F Ratio.
The wideband will help in the future to tell if a fuel pump is going out or if you have a ignition problem or the o2 is bad or if the afm is making the motor run too rich or lean-stuff like that. In other words it will really give you accurate and important information better than narrow band will. I would weld a bung in each bank before the cats and just run it in one of the 2 banks and put a plug in the other bung.If a issue arrises you can swap it to the other bank and compare the 2. A lot of people are unwilling to do this. But on my personal obd 1 cruiser it's really helped me out find issues big or small and it's easy to do. Wide band kits are cheap these days. I got a ebay kit and it works great. It's hard to get accross how useful the afr is on a obd1 cruiser. I'm probably starting to sound crazy endorsing a wideband setup though so I'll shut up now lol.