Ya don't really need 5 inch exhaust unless youre pushing some serious hp and flowing serious exhaust through the system. Yeah, it looks good and sounds good, but that's a bit overkill for a stock engine. Youre not really flowing huge amounts of exhaust towing at 2k RPMs. 4 inch is more than enough, and also keeps the exhaust velocity high for better efficiency. Definitely address the trans. The stock trans will only hold up for just so long, but it wont hold up at all with power adders. Been there, done that!