96 Suburban runing rich *UPDATE, PLEASE HELP*

I recently posted about my 1996 Suburban runing rich and i took the advice of those who posted and i thank you all for the help.  I believe i nearly have the issue completely resolved.  My problem stands now that i have 3 of the O2 sensors unpluged and the engine runs very well most of the time and with decent gas mileage but sometimes as im driving, all of  a suden,  the engine begins to misfire badly in the number 8 cylinder and i begin to smell the familular smell of the motor runing rich and my gas mileage goes down to only a few miles per gallon.  Sometimes it runs like this for a few minutes and sometimes for a few days, and when it begins to run normaly, it does it instantly, like someone fliped a switch and it is runing perfect again.  It goes back and forth from runing good to runing bad and i am looking for all help to try to trace down the problem to avoid spending hundreds i cant afford right now to take it to the shop.  All help is greatly appreciated.    Thanks,  Tyler

is this motor a vortec motor or is it tbi??

should be a vortec, so it sounds like you have an injecter playing games with you.

gm injectors after tbi are junk! sorry that doesnt help just had to say it.