360 Cat issue or something else?

With starting a new job, finalizing my parents estate, and just life in general, the most I get to do lately is look at my car on the way to and from. Every now and then, I get to devote some time to it. Case in point, my 2023 annual service started in November....

The good news is the car is back together after may cooling system issues, and an unscheduled belt change. Checked and rechecked everything going back together. Fired her up for the first time a few weeks ago. Car started and ran without issue...sans one. Exhaust on the left side has a slight "lumpy" sound...sort of like a high lift/long duration cam that I'd throw in a Chevy 350 back in the day. Didn't think much of it. No Check Engine lights or anything like that so, on to test drive. Checked the bank angle and it's at 660-662. So it seems timing isn't an issue. Test drive was uneventful...until it wasn't. All of a sudden, Check Engine comes on. No change in drivability though. Get home, check codes. Random multiple misfire/misfires on 5 through 8. Strange, cause it drove fine. I just attributed it to when I lightly cleaned the engine afterwords.

Went for another test drive later that night. No Check Engine lights, but when I came home, I opened the bonnet like normal, saw a tinge of pink under left heatshield I just made for the convertors. Right side was normal. There was some spirited driving, but none that should make the converter glow. Again, no Check Engine, or anything else strange. Figured I had a plug (new) or coil (new in 2016) acting up. Pulled the coils and plugs on the left side and check them. One coil spec'd different than the rest, so I swapped it with one of the good coils I changed out back in 2016. Put the car back together so it could sit a week while I took care of life.

So, here we are today. Windy beautiful day when most people should be out playing with there Ferrari instead of taking it apart like me. Anyway, I fire it up and take some thermals. Not what I expected...

All cylinders on the left side were about even with the exhaust temps off the head. Headers were within a few degrees of each other, so no fuel or ignition issues, but I still have the loppy V8 sound from the left side. Right exhaust sounds like a proper Ferrari though. So, I won't bore you with more storytime, but what do you think about the exhaust temps? Any ideas on the exhaust tone?

Car is a 99 with no precats, running original injectors, OEM headers, new plugs (2024), and newish (2016) coils. ECU tune w/delete for CAT ECU's and rear O2 sensors. Tune was also optimized for high flow cats which I am curently running AP 100 cell sport cats. As far as the timing goes, before I pulled the belts, the scribed marks on the rear of the cams all lined up with the caps, except one. It was just outside of the mark. When I put it back together, all four cams were lined up to the caps.

Link for exhaust sound
https://youtube.com/shorts/hd8NzadpxuQ?feature=share

676F Left cat inlet
858F Left cat outlet to muffler
660F Right cat inlet
706F Right cat outlet to muffler

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Left inlet
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Left outlet (side profile)

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Left outlet to muffler (top profile)

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Right inlet to cat
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Right outlet from cat to muffler

 

No codes.

LT/ST didn't look out of spec but I don't remember what they are. Will check that later

Car pulls strong to redline. Actually, stronger than before to be honest.

 

Might reach out to him as well. First order is pop the back covers off the heads and look at the cams just for S&G's.
Thermal showed each cylinder was registering around 200 or so just off the head, But just in case, there should be a box of new coils showing up any day.
As far as the other issues go, no grounds disturbed AFAIK...
Fuel was fine before, but filled up anyway from "quality" station. Same place I get for my other cars and didn't experience any issues.
Battery is on a tender and I've got a remote voltage gauge showing charge voltage as well as running voltage

 

Your stock tune or the Trev improved one? I've been running his tune for about a year now and everything was okay.

Common factor is timing....looks like I'm checking cams again. I did remove the plenum to have it powdercoated so I'll double check all the bolts etc to eliminate them being loose.

 

The coils were replaced in 2018 but I have a new set crossing the pond now, but I appreciate the offer! Pulled my old coils and spec'd them out just for giggles too.

 

Agree 100%...although Alec Baldwin might have issues with that statement! Anyway, the misfire codes are strange. Have come up twice, no change in drivability or engine tone. Now I know that the 'puter detects missfires that you gun and jet exposed ears don't but just seems odd that there is no change in character.

 

Yea, I see a phone call to Mark over a Sphere in my future....

 

only thing I took off was the plenum, but it is a 23 year old car too! Wonder if my SWAT buddy can get me a smoke grenade...

 

Have you priced brake cleaner lately? OMG, that stuff used to cost about 1$...now it's north of $3 for the cheap stuff!