At 4,500 rpm's you're just getting into the power band, so it would feel slow, even more so if it has stock rear gears. Between there and 6,500 is where you'll really feel the power, especially in the lower gears. However, 18K seems like a bunch of money for a 99 with those miles and poor paint. I bought a near perfect 01 with 22K on it for 16K just a couple of months ago. I don't remember the exact prices, but there have been some recent threads on this and it seems to me that most folks are paying about 12-14k for 99's with that kind of mileage, with good paint.