I have a 2004 Trailblazer EXT with 148000 miles on it. I have had an issue with power loss from the engine, it starts and idles great, but when driving it, it will go down the road, but it struggles to go. Around 20 to 30 miles per hour it has its most problems, but I can floor the gas pedal and it will eventually get up to speed. I have had it to the dealer and they have done the following, replaced the catalytic converter, replaced muffler, cleaned throttle body, and induction flush. I have personally changed spark plugs, fuel filter, air filter, CPAS, and I have cleaned the throttle body several times. The dealership is done with it, they don't know what is wrong with it and don't want to look at it anymore. I can fix it, if I know what is wrong with it, but at this point I have no idea what could be wrong with it. I asked the dealership to check the catalytic converter again and they act like they don't want to. This is my wife's vehicle and I really need to get this repaired, I would greatly appreciate any help.