Wideband AFR gurus come in

I have recently installed the PLX M300 wideband setup... for those of you who are familiar with this setup, it starts out reading 14.7 , and after approx 20-30 seconds, it starts increasing 16...17....18.."LEAN". To avoid any possible damage, I shut the car off. I find it highly unlikely my AFR is reaching those heights within the combustion chamber. I have read on other forums that at first the engine uses the air pump to compensate for heavier emissions. Does this apply to the 5.0? I have an 88 with 89 Mass Air system...
wideband is feeding a narrowband signal to ECU at pin 43 ( I replaced my left bank NB sensor). Any tips as to what to expect? Read sig for any mods - I have posted before on proper tuning procedures, however now I am leaning twords a tweecer.

as a side note: 20 HG vac constant, clean MAF, everything is calibrated to eachother, FP @ idle 45psi. Any other pointers?
I was going to replace my narrowband on the right bank anyways since I do not know its age, and I do not have a CEL to let me know if its junk.

Ive also read I need to install a 20ohm resistor in series with the heater circuit...is this the wire leading from the wideband controller to the ECU at pin 43???
THANKS

This afr was taken at idle- (initial useage) I simply wanted a hint as to what to do from here....would it be safe to let it idle out and see if the A9L corrects this? Or does the problem lie in my MAF meter not being able to adjust to increased air flow from the SC? I am getting a tweecer to log and mod my ECM. Until then I want to try and isolate the problem Thanks

I am in the middle of finishing a deal for a tweecer RT, I have shorty bbk headers, bbk hi flo hpipe,

wideband sensor is mounted in the "stock" bung on the drivers side hpipe down tubing before the cat.

Has anyone heard of simple MAF meter malfunction/incompatibility with a SC?
I have a 73mm CnL and I am being told to upgrade to a custom 80mm PRO-M.
I think my setup is too mild for a blow through type meter, but I am willing to listen to what people have to say. I am going to take the belt off the SC this weekend and try to find if I have any weak sensors. Thanks again

I have been in contact with PLX tech support- I will get back to you with the results. I am sending the unit back to be tested to rule it out / find the cause.

As a side note: PLX tech support is extremely helpful!