2000 sonata problems

are there any qualified hyundai mechanics that can help me without charging me an arm and a leg ? i have a 2000 sonata executive with the 2.5 litre twin cam motor...when i bought it secondhand it developed a sluggishness which was most noticeable around 40 kmh when under heavy throttle....i had the 90'000 km service done hoping to rectify the problem...all was well for a day and 200kms...then the sluggishness and faltering started again...i have since had the mass airflow sensor replaced....and now i've been told by my mechanic a genuine hyundai mass airflow sensor as well as the crank position sensor needs to be replaced....anyone else in australia having similar problems ???