Trying to get my 2001 Prius to 300k

It's a milestone I want to achieve. Right now the little baby blue beauty is sitting at almost 257k. Any advice to help me reach my goal? I can post my entire work history for those who are interested(I bought the car from the original owner at 97k).

Yesterday morning I had code p3191, p0301, and p0304 which I checked at AutoZone and later while driving home the CEL started flashing but went away within a few moments...my poor ole car was misfiring. Today I had all 4 spark plugs replaced as well as new ignition coils for cylinder 1 and 4. Drove it around for about 30 miles after picking it up from the shop and sometimes I would hear what I can only describe as a galloping rattle at around 30-40 mph but did not seem to increase in volume or timing when I accelerated up to 50 mph. The sound seems to come and go and not sure if I should take my car back to the shop and ask if they wouldn't mind taking a little peep since I just dropped $650 today(don't wanna be a dick to them, they seem like a nice honest mechanic family owned shop). Any idea what could be causing the noise besides the engine, perhaps a heat shield? I did have my oil replaced 200 miles ago if that info helps.

I wish I still lived in Portland, OR because I always took my car to Atomic Auto and they are hands down the absolute BEST ever.

Sorry if my post is long winded as it has been a long day and I really appreciate if anyone responds. This has been the best and most reliable car I have owned and I have driven it all over the gosh darn place and I just really, really would be incredibly happy to reach that 300k milestone.

Thanks!