Good spark plugs are not likely to make the car faster, but using the wrong spark plugs can affect the performance and cause problems. See this comment that I found (https://www.matthewsvolvosite.com/forums/viewtopic.php?t=23426). "I would only use Volvo plugs, not the "oem equivalent"...

Using the proper spark plug is important, as mentioned previously you won't gain any HP but you could actually lose some HP using improper plugs. Volvo vehicles notoriously reject aftermarket plugs but to each there own. I'm a true believer in using factory parts, especially something as cheap as sp...

Ha! Our beginning female mechanics make far fewer mistakes because they communicate before they come here, with a tale of “ my friend John told me to put potatoes in my transmission,now it doesn’t work” story The general consensus here is to drain and replace unknown ATF slowly, about 3 liter a time...