Just top it off. The octane level will average out, and should be high enough.

 

Finally got word back from the shop it is at now. They claim I have coils on cylinder #2 and #4 failing, but no codes have ever came up and swapping new coils in did nothing to help the problem. Pulled valve cover, cams and rockers in good condition apparently. Didn't mention anything about the valves themselves.
"The noise does not appear to be in the area of the cylinder head or in the lower area of the block. We feel the noise is related to a piston or wrist pin. The next step would be to remove the cylinder head and oil pan to gain access and remove the Pistons to inspect. We believe that cylinder #4 is the origin of this noise."

So, no mention of valves(or mention of them being a problem) and I asked about octane issues and they waved me off as that being nonsense and no way could be causing this.
Opinions?

 

Sounds like guesswork by a clueless shop.

A good mechanic will not need to pull the head to diagnose it.

Find another shop.

 

it was towed to another shop this afternoon. This time it is one picked out by my relatives who own and operate the largest salvage yard in my state. I trust they know where to take their cars for good service.

do you think my mistake of putting in 87 could've triggered this? Could it really be as simple as switching the gas to 93 or am I dreaming?

 

no, as much as I wish it could have for your sake...the difference between 87 and 91 octane is not substantial and the S has mechanisms in place to account for it.

 

I understand.. I knew it was a longshot was just trying to see if somehow I might've caused this to happen but it really looks like a case of really bad luck. Hopefully this shop finds a solution short of another rebuild to this.

 

This, $40 on amazon can get you a good one that will connect to your phone

 

Well I finally got my car back from the shop I took it to, they replaced 2 coils that they believed were failing as well but couldn't diagnose the engine because "it is too old and complicated for them" very disappointed. The car was near empty and I filled it all the way up with 93. Runs significantly better on the highway with no noises to speak of and idles better, but still ticking. Not sure what to do next.. Looking into buying a borescope

 

i might have missed this, but did anyone check the valve clearances?

also, what exactly was replaced in the engine rebuild?

 

last shop claimed it had nothing to do with the valve train, but no.. I highly doubt any of them bothered to actually check the clearances. I attached a picture of all the paperwork I have on the rebuild.