He might still have the original pipe, so you could put that back on it. The 'Y' split is what restricts the flow.
The bikes are built pretty good lately - I have both a newer and older Cag (both HF ... well, one's a NF

), and true, they are both PITA's, but fun to work on. Plus, with all the mods you can do on them, it'll keep you busy for a very long time. Lucky 7's are THE top-of-the-line of the Cagllari series bikes, but you have to know where to look to get them.
I got the air intake problem solved - go check the link in my sig ...
Recommendation for riding: find a big empty parking lot and set up some cones, or see if you have a local go-kart track that will let you ride there. The forum generally frowns upon talk of illegal street riding, so be careful out there ......