Hello and welcome to justanswer.
Does the engine seem to miss and pulsate, or just have a lack of power? Is the check engine light on while driving?
I assumed this was done I paid for a full tune up. What r u saying?
Some places only replace the plugs when doing a tuneup and charge extra for these other items. I just wanted to know what all was done, so I can help you better. I will just assume all of these parts have been replaced.
There are some other possibilities for the symptoms you have described. You could have a bad ignition coil, a weak fuel pump, or a restricted catalytic converter. The fuel pressure should be tested with a gauge connected to the engine. With the key on, engine off you should have 55-62 psi. If the fuel pressure is lower than specified, replace the fuel pump.
A muffler shop can test backpressure on the exhaust system to determine if the catalytic converter is restricted.
If the fuel pump and converter check out okay, this would most likely then mean that the ignition coil is bad.