Yep. Take a car in for a tune up and they get 7 cylinders tuned and firing like they should but one has other problems beyond a tune up. That is what you have here. If anything it should sound much worse then when you took it in if they did their job and got the engine tuned correctly given the issue with the #8. When I bought my 64' Conv. it was running on 5 cylinders and had no power. My dad and I drove 3 blocks from the guy I bought it from over to a Casey's parking lot and did a quick tune up. We knew from driving it before when we bought the car that it probably just needed plug wires, plugs. I think we adjusted the timing too. I drove it home an hour and half away. Changed the points out when I got home and not only did this thing have power but for the first time I found I had POSI because I almost wrecked the Conv. when it broke loose.
