Phone [Q] After flashing my HTC Sensation XL( slow wifi speed)

Hello! After i succeded rooted my HTC Sensation XL and flashed it into rom cmd9 i got this weird wifi connection [ fast browsing speed but very very poor speed in downloading files ] -- like 10
-20kbp/s downloading just a single file....

So i decided to change my rom and tested threemusketers rom but still nothing change in my DL speed .... Unlike when i first buy my HTC Sensation XL i have great DL speed [ Im using the same wifi connection till this time ]

So i got a chance to borrowed my friend unrooted HTC Sensation XL and tested it to the connection what im using it has a great DL speed likely 100-120kbp/s .....

im so really disapointed to my self what i
've done to my HTC Sensation XL, If you guys have a solution to my problem i would really highly apreciatted having you to help me...

P.S:
Sorry for my Bad english ( still learning )