I changed the air filter on my car two days ago at a nearby shop and ever since then I've noticed it loses power when I accelerate. Is it possible they installed it wrong or is it just a coincidence? The engine sounds normal, no weird noises.
It's not very likely that a poorly installed filter would cause power loss, honestly - if it were blocking airflow, you'd notice it when starting or hear the engine straining, not just during acceleration. It's probably just a coincidence or you already had that problem and only just noticed it; it could also be that they disconnected something without telling you (like an air sensor cable, for example) so the first thing would be to go back to the shop and ask them to check if they reconnected everything properly. If everything's connected and the filter is installed correctly, you probably need to diagnose something else - maybe a fuel change, worn spark plugs, or something with the fuel injection.
It could be a coincidence, but if the filter ended up misaligned (not sealing the edges properly), unfiltered air would get in and that does affect the combustion mixture - I went through something similar and it turned out the cover hadn't sealed properly. Go back to the shop and ask them to check that it's properly installed and sealed, it's just a five-minute job.
After changing the filter, the first thing I'd do is go back to the shop and ask them to check how it was installed. Sometimes the filter gets placed a bit crooked or without the housing sealed properly, and even though it doesn't completely block airflow, it does affect how air enters. The odd thing is that you say the engine sounds normal, so it doesn't seem like a total obstruction.
Now, there's something the others didn't mention: some new filters (especially the cheaper ones) come with slightly higher resistance than the originals. If you went from a worn-out filter to a new really dense one, it's possible your air flow sensor is getting a bit confused those first few days. Your car's computer needs to adapt the fuel injection. Usually this stabilizes on its own in a few days or miles, but if the power loss persists after a week, it's definitely not just that.
My recommendation is that you wait two or three more days driving normally, and if it's still the same, go back to the shop. Ask them to read the error codes with a diagnostic machine (if something's off, it would show up there). Also confirm they used the correct filter for your specific model, because sometimes they put in one that's similar but not identical.
Something like that happened to me with my car once, and it turned out the filter was installed backwards without anyone noticing, so the air was going in without actually passing through the filter material. The car's computer picks up on that and adjusts the fuel mixture, which gives you that power loss feeling you're describing. I'd tell you to go back to the shop and specifically ask them to check how the filter is seated in the housing, make sure the rubber seals are closing properly, and that nothing got twisted, because if that's wrong it's almost certainly the cause.
Changing the air filter can affect engine performance, but it depends a lot on how it was installed. If the filter isn't sealed properly in the housing, unfiltered air gets into the engine and the computer has to adjust the fuel mixture, which can result in a noticeable loss of power. There's also the possibility that they put it in backwards, which would block a good part of the normal airflow.
My advice is to go back to the shop and ask them to check the installation. Have them open the housing and verify that the filter is centered properly, with all the edges sealed correctly against the frame, and that the housing closes without forcing it. Sometimes people don't notice details like a slightly twisted filter or a displaced rubber gasket. If everything checks out there, then yeah it would be a coincidence, but it's worth ruling out the obvious first before you start looking at other engine stuff.
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