ive put new coil packs ,new spark plugs,manifold gaskets front and back and my 06 toyota avalon is still shaking,surging.loss of power engine light is on but when resetted car still does the above and also light will flash sometimes.
If the light is flashing, you’ve got a severe misfire which has the potential of damaging the catalytic converter(s)
It sounds like this problem present BEFORE you did all this work . . . ?
You can use a noid lite kit to make sure all the fuel injectors are being pulsed properly
You can also perform a wet and dry compression test . . . if a cylinder has extremely low compression, all those parts you mentioned won’t do a bit of good, in all likelihood
It’s also possible there is rodent damage to the wiring, perhaps going to a coil or injector
Have you heard of those tools I mentioned?
Are you car savvy?
If no, at least you can perform a very thorough visual inspection and hope you can see the cause of the problem