UK 355 rough running ? Help please

I doubt that is it but I cleaned most of the engine bay contacts with deoxit, then hit coated them with Stabilant to provide a corrosion barrier you can try that to clean them and see but I suspect its something else. I replaced my coils on my 348 and the car was peppier for sure and seemed smoother but what made a bigger difference was the ignition Modules. Using Bosch part number frond them form Porsche reseller for about $65 a piece but use heat sink compound on them if you do that.Not suggesting that's the issue or you do it just passing on info is all. Again coils and ignition made things better but were talking small increments here it sounds like you have a different issue if your losing banks etc. Try swapping ignition modules to different sides after the new coil are in if you still have a problem and see if the issue changes sides if you can tell that.

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Strange. Where did you buy it? I'll tell folks not to order from there next time.

 

This the one that doesnt work
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Thanks! That might explain their 3 star eBay rating.