o2 sensor question

[stock 87 t-type]

I recently bought my t and noticed no o2 sensor on the down pipe
or either manifold and a weld filled hole on the cat, and it idles like crap
above idle it runs strong

 

[82grandBeast]

idles like crap or idles like it has a mean ass cam in it?

 

["Turbo-T"]

02 sensor should be located on pass side header just before the turbo mount flange.

Wels filled hole on the cat...some aftermarket cats come with provisions for if your car has an air injection pump. If it doesnt the hole is filled.