Restricting is not the word.
Not optimal would be better.
Have you tried tuning your engine with the stock 60mm B16B TB or the B18CR 62mm TB??
Plus to point out peak HP figures are nothing without a useable torque curve.
The B16B 185ps (182hp) designed and built by honda with type R cams, intake, ported head and uprated exhaust to be the ultimate 1.6 performance engine in a hatch so why did they use the exact same 60mm TB as used in the B16A 160ps and 170ps engine???? Surely if a bigger throttle body was better for performance then honda would have used them.