Faulty PCV valve? Not surprised. The quality control for these 'consumable' automotive parts is atrocious (spark plugs may be the only exception). They can cripple a car's performance, but spotting a defective item is difficult. You really need to install your 'tune-up' parts one at a time. If the car's performance collapses, you know you've just installed a new-but-defective part. Moral: Buy only the best -- even though they're just 'routine maintenance' parts. Even then, be alert and be suspicious. The auto business is a low-margin enterprise. Even name-brand 'replacement parts' manufacturers have to skate close to the edge in order to keep their shareholders happy. p.s. They do a much better job when it comes to supplying parts for new cars b/c now there are new-vehicle warranty costs involved and their customers (the auto manufacturer) will pay more to keep those costs under control. In the auto biz, it's all about $$$. I will defer to others when it comes to your fuel pump circuitry. My thesis is all about making the system (your engine, along with its fuel and electrical systems) as simple as can be, so that problems much easier to diagnose. Once that's done, you can add back the complexity (emissions control equipment) as you see fit. If it were me, living in Panama and driving a carbureted 50-year-old classic, I'd limit that to the PCV system. All the rest of the 240Z's emissions control gear, viewed from a 2025 perspective, is -- not to put too fine point on it -- finicky crap.