[nicfranc]

Thanks everyone for your input I will go with the M&K.

My Cat is shot and I do not need it to pass NY inspection as the car is now 33 years old.
I will put a new Oxygen Sensor in while I am at it and with the Cat out I will have better access for my first attempt at a valve adjustment.

Will the Pre Muffler replacing the Cat affect how the engine runs ?
I suspect the back pressure will change sans Cat.
Does the CIS adjust for this or do I have to tweak something ?

It is my understanding from my reading these boards that there is no chip in a 1980 SC.

This is my first P car and I plan on slowly replacing worn parts but keeping it on the road
as much as possible in good weather.

Maybe down the road I will go with SSI's and a new muffler.

Thanks for all the support from this great community I could not do this without you.