P0333, P0328 and P0100 codes

[Chickensaur]

Hello, new to the forum 

Bought a Mk5 GTI last year, no obvious problems when I bought it. It sat for a few months while I got my license (had a permit at the time and no one to drive around with). During that time on a drive the check engine light came on, the codes being P0333, P0328, and P0100. According to my googling, it's both knock sensors and the MAF sensor that are causing the codes.
About a week ago the engine light went out on a drive to the store, but came back on after a couple of days.
The engine sounds fine, and it doesn't feel like it's lacking power. I'm going to take it to a shop soon to sort it out but was wondering if anyone here could help me out beforehand.
From what I looked into replacing the knock sensors is very costly in labor, afraid I'm gonna have to have it done.

[ROH ECHT]

Would seem unlikely that both knock sensors and the MAF all failed at the same time.
Would seem possible that their wiring may be causing the issue if they are all on the same circuit. But I do not recall them being on the same circuit.
If it were running quite rough from an air inlet leak, this would seem somewhat reasonable as to why the knock sensors and MAF sensor have coded at the same time. But as you said, it seems to run fine.
It may just be that some of its wiring connectors have developed corrosion while sitting and now require some cleaning.
And....it is possible there is more than one issue with it.

Hopefully you have selected a shop who will not just replace parts in hopes of resolving the issue__find the parts did not do so__and then tell you that it in fact it required further replacement of more and more parts. All having been done so as they took repeated stabs at fixing it by replacing parts, rather than diagnosing it in the beginning.

[Chickensaur]

Forgot to mention it did have a very rough start one morning and the air inlet hose had come off the engine cover when I looked under the hood, so intake leak could've been it, I don't know when it actually came off. I snapped it back into place. If it's just that then that's a relief. The intake duct that attaches to the front of the engine cover is also so worn it doesn't stay on, don't know if that'd be an issue.

Thank's a bunch for the reply!

[pudding]

The front intake snorkel doesn't really matter but the turbo to airbox hose is very important!  The engine definitely won't like that pipe falling off!