Downshifting on the highway (uphill grade)

[coolcat21]

I'm just wondering whether it's just my transmission-engine set (see my profile, i've got a jdm corolla with the yaris tranny-engine set) ...or if all yarii are like that.

Basically when (i'm at 50 mph) encountering a slight uphill grade...or even when i want to speed up on flat roads , i press on the gas , it upshifts to 3000 rpm .but there's barely any increase in speed (if road is flat then speed creeps up bit by bit ..slowwwwly ..........BUT if there's a slight incline...or worse..full uphill grade ....it just stays there ....)

Is it just my car or yours too ? Granted , my frame (CBA121) is slightly heavier than your yarii ....but it shouldnt' matter should it.

Also, I have a the factory stock skinny tyres (175/70/14) ...but are planning to replace it with 185/70/14 (this is one of the 2 spec labelled on the door).