Recently replaced turbo sensor, still jerking when increasing speed, lose hose?

What is your question?

PLEASE NOTE: I am completely ignorant on mechanics. I am mainly looking for suggestions on what I can have my mechanic check. I replaced the turbo sensor about a month ago, and yesterday as I was driving up a hill, the car lagged and would not downshift to increase speed. I don't know what to have my mechanic check- he had recently mentioned a lose hose that pops off and messes up the turbo. I had been experiencing random jerks for a few months, but chalked it up to 'normal' turbo-induced behavior. It turns out that some hose was lose and would disconnect, which messed with the turbo- accounting for the jerky shifting and boost lag. Also, the check engine light would come on when it disconnected- like every few weeks. To pass safety & emissions, I had to get the engine light off, so had the mechanic replace the hose. Light was still on, so he looked into it further and said we needed to replace the turbo sensor (again- if this is the wrong term, replace it with the correct one...) so we paid to have it replaced. Engine light shut off for about 2 months, then turned on again. That was a few weeks before the uphill lag mentioned above. --What is this hose that is slipping off, and how do I fix it? --Obviously, replacing the sensor didn't fix the lag issue- so what else could it be? (the issue being that upshifting it jerky, with a small lag- then recently exhibited the same issue while attempting to downshift while going up a hill.) --Keep in mind that I have babied this car; I have driven a lot of miles (it has around 120K), but I am hyper-vigilant about regular services and oil changes, tire rotation and replacement, etc. Please provide answers in very simple terms, or an explanation that a small child could understand. Thanks!