99 Yukon loss of power

Have a 99 GMC Yukon with 120K on it. It runs rough at first when starting when the weather is cold. No problem in the summer. Hesitates and chugs for the first few minutes.

Recently I've noticed a segnificant loss of power on steep inclines. Like 70% going up a 1/4 mile hill.

Normal driving (flat, even slight incline) it's fine.

Have a 99 GMC Yukon with 120K on it. It runs rough at first when starting when the weather is cold. No problem in the summer. Hesitates and chugs for the first few minutes.

Recently I've noticed a segnificant loss of power on steep inclines. Like 70% going up a 1/4 mile hill.

Normal driving (flat, even slight incline) it's fine.

Welcome on your first [post on AF

How is the tune up end?
What is the mileage and what kind of plugs?
Any engine miss fires?
Plugs and fuel filter and fuel pressure?
Any check engine lights or codes.