why is my car running like such a piece of shit?

My car runs on only the factory computer when not boosting, and before it ran fine, but now it runs like shit! I know this is going to be a pain in the ass to diagnose, but all I have changed is no egr lift sensor connection, and the ls throttle body, (and the AEBS manifold, but I know this isn't doing shit except it does produce an increase in top end power, under boost of course) and I don't have the factory idle control soleniod (86-87) vacuum lines connected. The only code is 12, egr lift sensor. I don't have the factory 02 sensor connected, instead I have a zeitronix wideband unit. The car idles incredibly fucking rich, like 11.3:1, and runs so rich under part throttle that if I rev it, it backfires as I let off the throttle! That is serious bullshit! When I connect the wideband controller's narrowband output to the factory 02 sensor wire, the car will cruise at 14.7:1, properly, but it has very weird, laggy throttle response, with the a/f going all over the rich end of the scale. (???) That seems to be reduced slightly when it warms up, but is still annoying enough for me to roll with the narrowband output disconnected from the factory computer. However, then I get shitty gas mileage. I don't get it. Maybe the LS throttle body is fucking with the part throttle fueling..but I would figure that the long term fuel trim under closed loop would gradually compensate? Also, the other reason why I don't like to cruise with the narrowband output connected is that I can boost with less than 1/3 throttle under 4Krpm, (closed loop) and then the factory computer starts leaning out against my supplemental injection system. That is not good for 2 reasons, 1, you want to be richer than stoich under boost, and 2, when you put the throttle in the same position before the turbo spools, you will running lean (soggy resonse). I know I can make it run a lot better because it used to run a lot better, before my radiator pissed coolant onto my turbo, etc, etc and burned the fuck out of my old harness and distributor.. I don't know, any of you guys got any ideas? I hate the factory system, it sucks a fat ass dick.
p.s. I like where the conversion harness shit is going, maybe my car will end up rolling with an uberdata modified integra ecu