a good set of headers and Y pipe are worth alot. Theres improvement there in those items but it works for now. with a baffle being loose in the muffler that might be causing a restriction.
if you would log the car you would be able to see if the intake setup or exhaust is a restriction by reading kpa. the lower the number the more restriction there is and this will hold back performance
as for times yes thats with seat time, however mph indicates the power of the vehicle which is were justin and i are looking at