Unsure what you might classify as printing speed, but sometimes I will turn off my heaters for cutting heat transfer vinyl, when doing so, I eliminate a lot of warmup time for the heaters and oftentimes I will forget to re-enable them for a vinyl/banner job. Only problem is the inks need the heat in order to bind to the material, so I end up with a job that starts a lot quicker, but then has tremendous banding and takes longer to cure. The print speed itself in this scenario is unaffected, but the actual warmup time gets cut down by about 5 minutes. So might want to check that.
Other than that, I can't think of anything that would speed up printing but denigrate quality outside of the RIP, unless you might've lost power for a long time and your printer reverted to defaults for bidirectional settings or something, but I've honestly never fooled with the printers options much and do most of my setup in Versaworks except for cut force and heaters. Sometimes I'll forget to specify a media type and will get a lower quality output due to improper profile, but that's something you should be fairly conscious about unless you might've reinstalled or updated your RIP recently (in which case it might've changed some quality settings/defaults on you).
Hope that gives you some ideas to start from!