In summary, no, not really. It kind of feel smoother when accelerating past 4000rpm to redline. I did replace my spark plugs at the same time, so whatever I feel could simply be fresh plugs. The good news is I'm able to run a larger gap with my spark plugs. I left them at the stock 0.028 inch gap and no misfires. Before if I ran anything over 0.024 inches I would get misfires in cylinder 6 at WOT. MPG does seem to be 1-2mpg higher as my 30min test drive on the highway shows 27-29 MPG. Again this could just be the news spark plugs. I do continue to feel slight shudder every 5-10 seconds when the car is at idle, but I have a feeling this is likely because of a vacuum leak around my intake boot.
(WOT = Wide Open Throttle)
Thoughts on the kit?
It certainly feel over priced and I knew that from the start, I just didn't want to deal with making a wiring harness from scratch... So yes, I'm paying extra from convenience. As well, the extra wiring kind of makes the engine bay look messy. I'm sure with a few black zip ties here and there I could clean it up, but I'll do that a few weeks from now once I'm confident that everything is working ok. I do really like the 1 piece mounting plate for each side of the engine. I pick the black color as I really don't like a flashy engine bay. The mount just look more OEM in one piece vs some other setups that have a separate mount for each cylinder. As for the wires they all look very OEM. The once thing I don't like is the length of the ground wire. It seems like it should be 1-2 inches longer so nothing is pulling on it. As the wiring is routed at this time, I'm sure a year from now I would be working on fixing broken ground wires.
How was the install itself?
ECS on their instructions claim this as a "easy install" and I do agree with that. The hardest part, as with everything on this S4, you spend more time moving stuff out of the way than you do with the actual installation of whatever part you are working on. Remove airbox, relocate coolant reservoir, remove old coils, install 6 bolt per mounting plate, press in the new coils, connect the wires, re-install airbox/coolant reservoir, and finally go for a test drive. So it's a rather easy install. I think it took my 2.5hrs to complete but I was going at slow pace.
Would I recommend it?
I would say that it is too early to tell. If you are bored and want to replace something with something "newer" because you got the itch... sure go for it. If your stock coils work without issue, then no, this would not be worth it for you. For me that cylinder 6 misfire is the main reason I replaced this as I wanted to see if it would help correct the misfires that seem to come back every 12-18 months.