Installing headers on 91 ranger and insatting y pipe is about 1/4 to short to con headers any suggestions

Could be catalytic con.

Either the wiring has worn out or broken or the fuse has been damaged, you need to check out both.

Most likely it is the air condition pipe that has the condensate (moisture) on the pipe. When the engine has stopped and if the air con has been running you may hear the air con gas/fluid in the pipe.

You will need to have a bung welded into the header so you can hook it back up.

the first thing i\I would try is to replace the Oxygen sensor...this happened to me on my 91 F150 pickup and that cured it..

the filler hose has a vent pipe or hose inside of it or alongside of it. If the vent hose is blocked, you can't get the air out of the tank while it is filling so you end up with "Spitback" or pump kick off.

The aftermarket unit may not have a vent hose. Did the original pipe have an internal vent hose or external?

This may be a dumb suggestion, but have you tried changing out the battery? I had a similar problem and changed my solenoid, cleaned all grounds and wiring connections and after all that it ended up that a cell was shorting out in the battery. Something to check out anyways. Good luck and hope this helps.

most o2 sensors are located in the exhaust pipe at the cat con

change the oil just before the test and get the Cat as hot as u can.

If you have strong valve springs they shouldnt be floating... What kind of mufflers? They could be adding backpressure, Id go with a straight through mufler.