Rough idle and blinking eng light. did oil change but dealer says need ignition coil $1350

Get the OBD codes read as will identify the problem sensor/component

code p 0300 is random miosfires
indicates problem injectors from dirty fuel
Try a can of quality injector cleaner first in a tank to see it it smooths out
other causes include
ignition coil/s
HT leads
Plugs
Wiring but as it runs good at rpm and you have covered the rest , it is most probably sticking injector tips so use the cleaner or have the injectors serviced

Here's a link to your code.

check coil packs

Whats the actual code?

Rough idle, flashing CEL, low power would indicate a faulty ignition coil. A armchair diagnosis would be to replace the ignition coil. You'll have to swap the the contact stems (rubber conductors between the coils and the spark plugs) and the igniter module.

Simple task requiring a 10 mm socket and ratchet, a 10mm box end wrench, a T-15 torx bit with adapter and a new coil pack. Cost around $100 and takes a half-hour.

well the light is blinking because of the misfire it is setting a P0300 engine missfire detected, a plugged fuel injector will cause that misfire or a incorrectly gapped spark plug, also a bad egr valve will cause a rough idle and acceleration problems.but for a correct fix with out throwing parts at it will have to be done by a pro

Blinking light means severe eng misfire, Check coils and ignition module

check the compressions ---NO4 ?? but i think you may be right about the ECU

Ok, i would ave the ignition coil pack tested for its operational valve asap if possible. this is either an ignition coil pack issue or, a bad ECM. the ECM controls the ignition timing in this vehicle so, the problem will be there if the crank shaft sensor and cam sensors are ok.

I would pull the trouble codes asap as well. this will help diagnosis this issue correctly. this can be done at a local auto zone or a local mechanics shop as well.