re: forza 5 or forza horizon 2

I haven't played the original Horizon in awhile so it's a little fuzzy, but when I say no tuning, I literally mean no tuning menu. The upgrade game-mechanic is still there, identical to the regular Forza games. So you can still install new upgraded engine/suspension parts, do engine/drivetrain swaps, new tires & wheels, etc.

What you couldn't do in the original Horizon was get down into the really detailed adjustments of things like gear ratios, camber, caster, rebound, spring rates, rolls bars, etc.

ETA - when talking Forza, "upgrade" and "tuning" are two connected, but ultimately independent game mechanics. In Horizon 1 the devs were very clear that there would be upgrades, but no tuning. I expect the same in Horizon 2.