Hi guys, I’m looking at buying a 2012 speed3 with 70k miles and a rebuilt title that is running extremely rough. My friend bought it from a auction and he tells me it appears to have a new long block, he has replaced hpfp, fuel pump in tank, coils, plugs, compression tested good. The car idles fine and can redline it in neutral, in gear moving it stutters/bucks/ whatever you can think of above 2k rpm in every gear. It does throw a cylinder 4 misfire. Where do I start at diagnosing this? Car idles amazing but under load it starts to do these problems. I’m thinking turbo or ecu? Could the car need tuned? Any help would be appreciated as I have never owned a Mazda. As I said any input is helpful. Thanks