Pontiac Fieros came with a 2.8L V-6 rated for 140 HP. GM later made a 3.4L V-6 using the same heads with similar intake and exhaust. This engine was rated for 160 HP. The displacement increased by 21% and HP increased by 14%

I contemplated bore and stroking a 2.3L DOHC Quad 4 to 2.6L which is a 13% increase in displacement. I bought the DynaSIM software to check this out. It predicted an increase in HP from 191 to 205 or 7%. When you put a bigger displacement engine on the same intake, same heads, same cam and same exhaust, the volumetric efficiencies go down and you don't get as much of a HP from the displacement increase as you you might hope.

Based on the ECM calibration data that In-Tech posted, the 350 TPI has a peak air flow of 1876 lbs/hr at 5600 rpm (73.8 volumetric efficiency) 100 kPa and 30 'F ambient. With an air fuel ratio of 12.5:1 the fuel requirement per injector is 18.8 lbs/hr. The OEM 350 TPI injectors are 22 lbs/hr. A 383 has 9.4% more displacement than a 350. Steveo's recommendation of 24-26 lb/hr injectors feels right to me