You do not want more peak horsepower you want more torque in the towing RPM range.
Assuming these numbers are accurate:
1FZ-FE:
max power: 158kw @ 4600rpm = 212hp @ 4600rpm
max torque: 373nM @ 3200rpm = 276tq @ 3200rpm
276 / 4.5 = 61.3 lb/ft torque per liter @ 3200rpm
The early 1uz-fe makes 260 (over-rated) / 4.0 = 65 lb/ft torque per liter @ 4400rpm
Long tube SMALL diameter headers with good merge collectors and SMALL secondary pipes along with a bump in compression (premium would probably be needed) could get you to your goals. If the valve angle and head design is similar to the 3UZ-FE you could possibly copy the cam timing AT THE VVTi SPECIFIC numbers for that same engine at 3200rpm. The 3UZ-FE as found in the 2001+ GS430 is rated 325lb/ft = 76 lb/tq at 3400rpm.
Unfortunately, this higher compression would possibly cause problems in a heavier vehicle used for towing.
The long tube headers/exhaust I describe above may give you the gains by themselves you want. If you pick up 7 lb/ft per liter you gain 31 lb/ft.
Other choices would be LOW boost supercharging or turbocharging. This would be a specifically engineered system to give say 3psi of boost. You could use one of the TRD supercharger systems and change the pulleys to get your target.
3psi in the range you are targeting should give you a gain in the range of 50-60 lb/ft possibly more.
Assuming these numbers are accurate:
1FZ-FE:
max power: 158kw @ 4600rpm = 212hp @ 4600rpm
max torque: 373nM @ 3200rpm = 276tq @ 3200rpm
276 / 4.5 = 61.3 lb/ft torque per liter @ 3200rpm
The early 1uz-fe makes 260 (over-rated) / 4.0 = 65 lb/ft torque per liter @ 4400rpm
Long tube SMALL diameter headers with good merge collectors and SMALL secondary pipes along with a bump in compression (premium would probably be needed) could get you to your goals. If the valve angle and head design is similar to the 3UZ-FE you could possibly copy the cam timing AT THE VVTi SPECIFIC numbers for that same engine at 3200rpm. The 3UZ-FE as found in the 2001+ GS430 is rated 325lb/ft = 76 lb/tq at 3400rpm.
Unfortunately, this higher compression would possibly cause problems in a heavier vehicle used for towing.
The long tube headers/exhaust I describe above may give you the gains by themselves you want. If you pick up 7 lb/ft per liter you gain 31 lb/ft.
Other choices would be LOW boost supercharging or turbocharging. This would be a specifically engineered system to give say 3psi of boost. You could use one of the TRD supercharger systems and change the pulleys to get your target.
3psi in the range you are targeting should give you a gain in the range of 50-60 lb/ft possibly more.
