4cyl 80 problems

[ARTHUR, KEITH]

hello, 

After wresting with my mothers oxygens sensor for a while i finally got it off.  But unfortunally whoever put it on crossed threaded it, preventing me from being able to put the new one on.  What are my options for fixing this. Can a tap be used to fix the threads or is a new down pipe in order??(hope not)

Also the differential pressure regulator is not responding to changes made to the adjustment screw.  My meter reads around 22ma all the time and will not change if i turn the screw.  If i lean the mixture the engine will start to rev up and down and will almost cut off.  Will replacing that oxygen sensor fix this(i doubt it will)?

Thanks for any help!  

Keith