i had the same experience 5yrs ago with my 1st gtr...
after 2 other tuners played around with my car i took it to jim as well, he laughed at the mapping then started tuning it. he gave me the keys & said:
"take it for a drive, if u dont like it dont pay"
so i took it for a drive & when i returned i couldnt wipe the smile off my face, he only picked 35awkw on the tune & SAME BOOST LEVEL
u pay for what u get, he isnt cheap but well worth every cent - good luck with your car.