svx going downward when starts uphill

94 red FWD , only 80k miles, all other shifting is good.

It behaves like a munual tranny car when starts uphill, it will go downward at various speed depending on how steep the road is before it actually moves upward from stop. If the hill is too steep and I push the gas too much, I feel like smelling the clutch burning.

Is it a transmission problem or sth else?

I have bought stage 1 chip and smallcar **** kit, but haven't put them in.

Thanks!