Have you considered getting new, really really skinny friends ?

Have you considered getting some bigger friends and train them to jump out and push in those types of situations ?

I would suggest you check your fuel filters, start of fuel delivery and chain stretch. Five months is enough time to grow algae or get water in the tank which might move to another spot when at a real incline... but since you did not get the turbo rear end I think you should have enough power to climb that hill in low if your engine is in normal shape.