328i n26 issues

hello, i recently bought a 2013 328i with the n26 motor, and the guy i had bought it from had told me all it had was an intake and tune. no big deal, i wanted to just convert back to stock and build it as my own. a couple weeks into driving, it would go into a “limp mode” and shut the turbo off, but it would say “cont. driving possible” so i have been, but i took a better look when i was free, and discovered there was no tune, but it did have the CAI (obviously im not checking the tuning as im buying it), and it turned out to have a catless downpipe he failed to mention. i had thought the limp mode and the jerking around was due to the rich codes and camshaft position sensor codes, causing fuel to burn up the cat, but turns out there wasnt one to begin with. i was told from a bmw tech friend of mine it is probably the timing chain, but wanted to come on here and see if anyone had any input to give in? any thoughts are appreciated