OK,I dug around a little and this is what I gather..
Code 81 says that you have a problem with your air managment system...More specific,I think it's your Thermactor air diverter (TAD) which is solenoid located behind your passenger strut tower,kinda down in there with a couple of small hoses connected to it.It's seated right next to another solenoid exactly like it (TAB).TAD is closest to your motor and TAB is closer to the fender.Do you still have your emissions stuff still hooked up?If you don't,then all I typed it worthless!
Code 33 seems to be a EGR code...There is a problem with the valve or sensor...
Codes 41 and 91 seem to go hand and hand when you are getting a lean condition...I had these codes and it seems that they were being cause by the TAD solenoid which had failed on my car and was letting excessive air into the system...that was making the O2 sensors incorrectly read a lean condition because of the excessive air that the TAD was allowing through.
41 and 91 could also be because of a problem in the fuel system...pump on it's way out,clogged filter....etc...
Any drivability or idle symptoms?
Hope some of this helps in some way...good luck-Milt