Originally Posted by SuzukiQ
Then again, that's another idea.
You mention the high mileage (well high to me as I'm in the UK) and I'm just wondering, might be worth trying a carbon clean on the engine?
good luck, quickest way to kill an engine doing that. Engines rely on carbon build up above the top piston ring to seal properly. Removing carbon in an engine with that mileage is asking for an increase in oil consumption and more issues.
My 2c, check the basics, when did it last get plugs? clean the lances/leads, air filter element, MAF clean with a good aerosol MAF cleaner?
Lot of times the basic stuff causes all sorts of issues. Your symptoms could be multiple causes, MAF and CKP and CMP sensors among the long list. Shotgun part changing is not going to help, and will only cost more money. Do the basic checks, maybe a throttle body clean.
Check all the lines and hoses for cracks, its always possible that a vac line has a small split that opens up at a certain vibration or rev range, this will certainly give you these symptoms.
As will a clogged PCV, the EVAP canister cycling etc. you might even find its when a purge solenoid opens and there is a vac leak causing revs to drop. EGR can also cause issues. When was this cleaned last?
see, lots to do that won't cost much money, (hey, whats a set of plugs worth if it hasn't had any in 10k miles)
just a bit of time and good learning for you finding where everything goes. Give it an Xmas prezzie, do some maint on it.