Shuddering, Chugging Acceleration

[Galizzle]

I have a 2007 Versa basic model with the power pack, 6-speed hatch. I bought it in 2006 - it was the first Versa to hit the local dealership when they were introduced. I knew it was dumb to buy the first model, but I wanted the 4-door hatch and had Nissan brand loyalty from my history with Sentras (1987, 1990 and 1995). I even sold Nissans for a while.

I also have a love/hate relationship with my car.

Tire pressure monitor issue - check.
Hubcaps falling off issue - check.
Door handle falling off issue - check.
Oxygen sensor issue - check.

And then other probably standard stuff...

It has 105k miles on it. I just had the control arm and the starter replaced. After the starter was replaced, I noticed that acceleration between first and fourth gear was kinda..."hiccup-y" let's say. Hard to tell on rough roads, but certainly not smooth. Took it back to the (well-regarded and seemingly reliable) mechanic who did the starter. It took them a bit to feel it, but then when they did, they said they didn't know, but perhaps the clutch? No check engine light, no codes. They kept it for a bit longer, and then gave it back with a quote to replace the clutch, but also said they really didn't know, and that I needed to wait for it to get worse.

It steadily got worse, pretty much immediately. I found another mechanic for a second opinion, since it's gonna cost $1250 to replace the clutch, and if I'm going to do that, I would rather know that it's *for sure* the real problem.

The new guy revved my engine, and said he felt definitively it was NOT the clutch. My clutch seems fine, is not slipping, etc.

It "feels" like a fuel pump or fuel supply (as in inconsistent) issue...it chugs like it's not getting enough gas, but I don't feel it in the pedal. It doesn't feel nuts-and-bolts mechanical, is what I mean. It progressively got worse as the new mechanic drove it. The next day, he said he thought he had it figured out - the Mass Air Flow Sensor needed replaced. $425. I went to pick it up, he said it ran a lot better after the MAFS was replaced...but when I drove it away, it was worse than when I left it. I went back and asked if it needed time to re-calibrate, and he said it shouldn't.

I haven't heard anything more today. Thoughts?