The Bullitt runs fine for what it has under the hood. High 13s is very respectable from a little 281 inch engine,off the dealers lot. Go back and see how strong 67 Mustangs where with the old Hi-Po 289,or the 69-70 Boss 302. But one thing that gets me is why the power drops off at 4800 RPM. Is it the heads or mild cam timing you think?