There are no power levels shown after freiza saga. But I know the power levels that Akira Toriyama's DBZ power level site mentioned these:
Imperfect Cell - 18,000,000
Piccolo [after reuniting with Kami] - 34,000,000
Android 17 - 30,000,000
Piccolo - 34,000,000
Piccolo [worn out] - 30,000,000
Imperfect Cell [after sucking the life out of many humans] - 34,000,000
Android 16 - 34,000,000
2nd form Cell - 58,000,000
Tien [neo-tri beam] - 12,000,000
2nd form Cell - 58,000,000
Super Vegeta - 62,000,000
Super Trunks - 60,000,000
Krillin - 5,000,000
Android 18 - 30,000,000
Perfect Cell - 95,000,000
Super Vegeta - 62,000,000
Super Vegeta [final flash] - 78,557,000
Perfect Cell - 95,000,000
Ultra Trunks - 98,225,210 [with slow speed]
Mister Hercule Satan - 10
Perfect Cell - 95,000,000
Super Saiyan Goku - 80,000,000
Perfect Cell [full power] - 145,000,000
Super Saiyan Goku [full power] - 140,000,000
Perfect Cell [after eating the senzu bean Goku gave him] - 165,000,000
Super Saiyan Gohan - 150,000,000
Cell juniors - 165,000,000
Super Saiyan Goku [battle worn] - 80,000,000
Super Vegeta [after training in the hyperbolic time chamber] - 120,000,000
Super Trunks [after training in the hyperbolic time chamber] - 115,000,000
Super Piccolo [after training in the hyperbolic time chamber] - 105,000,000
Krillin - 5,000,000
Tien - 5,400,000
Yamcha - 4,500,000
Super Saiyan 2 Gohan - 300,000,000
Perfect Cell [full power] - 191,304,000
Perfect Buff Cell - 201,456,040
Super Perfect Cell - 227,000,000
Super Saiyan 2 Gohan [injured] - 220,000,000
Super Perfect Cell [solar kamehameha] - 280,000,000
Super Saiyan 2 Gohan [father-son kamehameha] - 300,000,000
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Gohan is 12 years old in the Cell Saga
Sayian saga frezia saga trunks saga andriod saga cell saga buu saga
14,000 during the beginning of the Namek Saga, 27,000 after Guru awakens his power, 650,000 when Piccolo is fighting Frieza, 4,000,000 during the Android Saga, 23,000,000 as a SSJ after training in the Time Chamber, 35,000,000 as a SJJ2 while fighting Perfect Cell, 33,000,000 at the beginning of the Buu Saga, 9,000,000 during the Baby Saga, 27,000,000 as a SSJ during the Baby Saga, 50,000,000 as a SSJ2 during the Baby Saga, and 72,000,000 as a SSJ during the Super #17 Saga.
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Yes. In cell saga piccolo is even stronger than goku when fighting with cell for the first time,so he must be stronger than frieza.