Good writeup. One caution from having done this on a couple boxes: test stability after flipping ASPM on, especially with NVMe drives in the mix. There is a known class of Linux kernel PCIe ASPM bugs where L1/L1.1 substates cause certain NVMe (and some USB3) controllers to drop out under load, especially on older Intel platforms. If a boot drive starts acting flaky after enabling this, ASPM is worth reverting before chasing anything else.