Originally Posted by Rob Edwards

I wonder whether it's chip-related. Do you have the MAF screens and Ken's other recommendations? Colder plugs? 89+ octane?

Recommendations (from liftbars.com):
- Rebuilt MAF
- New knock sensors
- New CPS (crank position sensor)
- New TPS (throttle position switch)
- New hall sensor (cam position)
- Cam timing: 0° (-2|0 cold, PK32V'r)
- New OEM O2 sensor (not universal)
- Bosch WR5DC (7992) spark plugs
Required:
- S4 camshafts
- MAF screens installed
- 24# injectors (special o-ring)

I can still pop an LH and a known good MAF in the mail later today, am gone for a week starting tomorrow. I know it would be rich with the 24's but a good O2 sensor might get it close enough to at least run semi-normally (?)

Originally Posted by JET951

The glowing cats bit , reminds me of the 1989 > 928S4/GT/GTS that have old age trouble with their Exhaust Temp Monitoring system ( ETM ) ,that cuts out the ignition on one ignition bank ( kills one coil /module)

So if its a 1988 year type then there is no ETM , but it doesn't mean you do not have an issue with ignition on one coil bank , and yes they do still idle ( very low ) running on 4 cylinders( which makes the cats glow ,because of raw fuel still being injected) & yes they very much feel like they are being pulled back

Quick check for you to do with the engine idling }

Disconnect one of the two mutiplugs from the ignition modules ( next to the engine lid lower catch)for just a few seconds , reconnect then disconnect the other , again just for a few seconds ( this just stops their relevant coils) , if both ignition modules/coils are working then you will see little no difference in disconnection one as compared to disconnecting the other , meaning on a 928S4 that is idling at the correct RPM , all that happens is a drop in RPM , the idle control motor compensates immediately and raises the RPM , mild vibration from the imbalance , but the engine still idles , so in a case where both ignition banks are correct you get same result with disconnecting either module

Now if one module is not working , if you disconnect this one ( multi plug ) you will see do difference at all , because its not working , however if you then disconnect the other one then the engine cuts out , because its the only one working

And yes we see a few ignition modules play up every year( be it 944S2 , 928S4 , 964 etc etc ) as they reach old age & yes only replace with the correct Bosch type , because the non Bosch ones give us the most trouble

Ignition module 928 602 706 01 ) Bosch 0 227 100 124

Originally Posted by PorKen

Try plugging in the CO adjuster I include with the S4 chips. Turn it CCW a few turns (ships at 382 ohms).