So, when Han meets Luke and tells him that the Milenium Falcon is super fast and "made the Kessel run in less than 12 parsecs" guess what? He was full of it.
Here's why:
Han Solo is a scoundrel, a thief, and a liar. The Falcon breaks down almost every time they take off. Chewie spends weeks fixing the ship while they are hanging out on Hoth, and it's still beat to crap when they get to Cloud City.
The Milenium Falcon is a slow, outdated, worn down, piece of crap when pieces added on to an already crappy generic frieghter. I get that we want the Falcon to be a glorious ship, but are we really gullible enough to take Han at his word? I'm not.