2001 honda civic ex with 270,000miles and counting got one or two problems?

if you are driving and decided to hit the gas to go faster (like getting on the highway and someone wont get over so you hit the gas hopeing to get up to speed quick) now when you hit the gas like that the engine and rpms will go up but vehicle speed wont move until about 5 seconds in and will catch and take but when you drive normal and dont have to hit hard there is no problem. Also my wife the other day said while drivng at a constant speed she notice the rpms going up and down a bit like.5-1 and the engine following but speed staying the same so any advice will be nice it is getting close to 300,000miles and have alot of plans on maintenace when i get time such as all knew fluids and all new filters and plug and wires. Now i think some of the issues might be with plug and wires also need to replace o2 sensors wich might have a affect to but was wondering what is everyone else thinks about this

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