how many O2 sensors?
 

i have a 93 and i got one o2 sensor by the down pipe now the hollow cat that was sent by begi has two holes for o2 sensors. I dont have anymore sensors so am i suppose to install some in there or just plug these up? if i am gonna plug these up does any one know the bolt size?

also no mater how i try i cant get the final nut on the turbo to the manifold.

I got the top two and the bottom one i got the one on the front towards the fan but i cant get the one towards the firewall is there some speacil trick for this?

Pretty sure the plug size is m18x1.25
I run the stock sensors and the wideband and i have a bung for a dyno wideband as well. So 4 bungs total with 3 sensors.

extra holes are just that - extras for widebands and dynos etc. plug all the ones you don't need.
As to the bolts, what worked best for me (greddy kit which has a few bolts that seem impossible to get to) was to assemble the manifold, turbo and downpipe as one out of the car so I could get at it all from every angle, then disconnect the exhaust, with the help of another, snake the whole assembly into the motor, bolt it onto the head, and then re-attach the exhaust.

You can sometimes get O2 bung plugs from an exhaust shop if they weren't included with the exhaust parts.

Try threading it while the other 3 nuts are loose. If you give the turbo some space away from the manifold, you might be able to sneak the last nut into position over the stud. Then, you tighten all four of them down in rotation.

Worked for me anyway.