My new-to-me '78 P337H has pressurized mags (PMs) that aren't original. The turbo outlet "plenum" was tapped and a hose was connected from there to the PMs, with an in-line filter. I found no mention of PMs in the log books (its possible I missed it). That said, I flew it home at 17.5K and the engines were smooth as glass.
Anyone wanting some photos of the system, shoot me a PM.
My understanding is the T337 had PMs, but the P337 did not, for whatever reason. T337 is certified to something like 30K, whereas P337 is limited to 20K. Did not having PMs cause the ceiling to be 10,000 lower for P-series?
If I flew my P337 above FL20, even a little, would the FAA come crash my door down? I understand the cabin altitude restrictions.
Right now I have a Uavionix ADS-B tail beacon that has 978 UAT, meaning a hard altitude limit of 18k. Thought about selling it and upgrading the GTX330 to GTX330ES, which would give me 1090ES ADS-B with no altitude limitations. Not sure its worth it, even at low/no cost, just to gain 2k in possible altitude. And its not really even 2k more, because you won't be flying westerly headings at FL20 very often, so FL19 eastbound is likely the highest you'll go. Hope that made sense!
If I knew I could go to say, FL22-24 occasionally, it would be far more tempting to upgrade the ADS-B out.