right now he running stock motor with stock boost. beside having a hks smf intake. maybe his filter wasn't good anymore or dirty. does it has to do with the spark plug also?

normally he said that he can shift gear and pick up smoothy. now when he ready to put on gear seem to be the supra is working so hard and it shake like about to die or bogging every gear, after 4th gear to 5th is okay.

is this problem can be fixed easy, beside taking to the shop for more cost..?