ok, got the car back...runs like a new car.
going by what he told me here:
he said there was quite a bit of carbon build up, all cleaned up now...based on Ron's advice, i got the oil changed (synthetic oil and quality filters)...the back plate is not worth doing, just ignore it...brakes are all good otherwise...new plugs installed...new flex pipe installed...total price $548 taxes in.
in comparison, the dealership quoted me $483 plus tax (546 tax in) for just the carbon cleaning plug change)...they also quoted me around the same price for the flex pipe replacement...so i got everything done at the indie for half what the dealer charged...as well, the dealer told me i'd need new wheel bearings (no idea how much they charge for those) when replacing the back plates (which everyone agrees isn't worth bothering with)...and they also quoted me $1443 for a front/rear brake job...even just a front/rear brake service, they quoted me $238 plus tax (dealer said they were fine, don't need it)...lastly, dealer said if the carbon cleaning and plug change didn't fix all issues (rough idle, stalling, CEL code, etc), then i'd need to get the intake removed, cleaned and injectors replaced...from what i can tell, the car is perfect now.
would i still recommend a Kia vehicle??...sure, just get an indie to do the service on it.
it's going to be a rare occurrence for me to ever return to the dealer (unless i'm getting something out of it).