FYI: those are too big for a stock, or under 300hp car.
The tires themselves should fit, but you may need spacers. It depends what rim size they are mounted to.
You should not be having a tick on acceleration. That would most likely be detonation due to bad gas or a bad tune.
How did you turn off the CEL after adding the o/r mid pipe?
You need to figure out what the car will be doing. If there is any type of rain or longevity questions, stay away from hoosier. Mine look like slicks after a few track passes.
I do not notice an issue with 275's in the front. They fill the area well and give amazing traction around corners.
As for the tires, stick with the Nitto 555 series. It's a pretty cheap tire for being performance.
Did you happen to look and see if the shifter looks stock?
I'm not joking when I say I have to really push sometimes to get my MGW into gear. It doesn't always feel normal.