Problems With Sonata 2003 Gls V6

I have purchased the sonata 2003 V6 GLS, after 1000 mills the car started experiencing loss of power and when going up hill in third gear around 30-35 mills per hour, loss of RPM and power, adding gas would not result in addition of RPM and power, the car would increase speed slowly and when reached to around 40-45 mills per hour the RPM would suddenly go height, still in third gear, then switched to fourth gear. In addition spars have black carbon deposit on the inside of the plug, not on the conductor and insulator. Recently the car is bucking on the highway every now and then. Went to two dealers, computer does not show any code and they are dismissing all this as something being wrong with the car. ANY IDEA?
Thanks.
Eli

I would keep taking it back, make them ride with you to show them the problem.

could be a MAF or MAP problem.

maybe TPS problem. or o2 sensor problem. just tell them to check all the sensors.

After attending the West Palm Beach Auto Show today, the '04 Sonata LX is now on my short list.

You might want to check Edmunds.com's Town Hall posts for ideas on your problem. This sounds familar... I don't recall what it was though.

fuel injection cleaning,preferbly profetional one,bucking,loss of power,are all syptoms of clogged fuel injectors,also your air filter,and plugs