Dealer Financing vs. Credit Union

[gtrplayer]

Ok...I'm pre-approved at a price and a solid interest rate.

What happens when I go into the "finance" office at the dealer and he/she says, "I can get you 4.5% instead of your 6.4%"

I want NO addons, NO exteded stuff, NO protection, NO insurance...JUST the amount listed on the order that we agreed upon. Is that possible...?? Or is the dealerships financing a scam??

He also told me he can get this rate IF I have good credit! My credit is good, but then who defines "good".... now he's ran my credit report numerous times (correct?) in an effort to "shop" me the "best" rate and comes back with 6.0%.... I HAD 6.4 anyway with MY credit union???

Is it worth it to go through all that IF I'm already approved?? WHat is the scam here????

Thanks!