it's because SOHC vtec sucks.

it really doesn't do much and it was just there to give the car a slightly extended torque curve. the end result is a torque curve that is smoother, but not specifiacally that much better.

all in all you aren't doing something that is wise, a manual converion will cost you money in two ways, first to do the conversion, second when you sell the car it will be worth less money. i say sell this car and either buy a manual accord or buy a newer car with more balls than a SOHC I4