Oxygen censor
 

My '87 uses multi-port EFI. My oxygen censor is completly gone due to the header I added and yet somehow it still runs, though it stalls out at low idle, usually towards the end of the day. Can anyone explain that?

without the input from teh oxygen sensor it is running in limp mode. it will get porr gas mileage, poor performance and poor life expectancy. the computer is just using pre programmed numbers just to get the engine running. get an o2 sensor bung and drill a hole in the collector of the header and weld the bung in and put the o2 sensor back, it will run much better and get better gas mileage.

x2 dont let this sit for much longer