The factory XB fuel injectors are great for a stock or mildly modified engine, but they can begin to fall short at stock fuel pressure after about 110 hp (at the wheel). An easy first upgrade is to install a higher pressure regulator. Late 90’s Dodge Caravans (specifically a 1996 3.8L OHV Caravan, other models as well) use the same style but higher pressure regulator that holds ~60 psi, about 10psi higher than stock, or you can buy a 65 psi regulator from EBR.
The factory in-tank pressure regulator design works well for naturally aspirated motors, but when you increase the manifold pressure above atmospheric, the dynamic fuel pressure at the tip of the injector decreases. To properly fuel an forced induction XB using the factory ECM, it is much easier to remove the in-tank fuel pressure regulator and install an external, boost-referenced regulator.
Once I hit 126 hp and 100 ft/lbs, I had adjusted my fuel pressure, via the external regulator, up to 65 psi and several of my fuel map values were maxed out.The stock XB injectors were no longer supplying the volume of fuel the motor needed. I wanted to maintain a dynamic 50 psi fuel pressure to make things as easy on the fuel pump as possible, so I looked for fuel injectors that were 40% larger. The V-rod Destroyer injectors are 41% larger and they will fit in the XB manifold with a little modification.
When I upgraded the internals to forged pistons and dropped the compression ratio from stock, I was shooting for 160-180hp, so I tried these Siemens Deka injectors:
They are 60lb/hr and they drop right in to the XB manifolds. They have the exact same body as the stock XB injectors and they flow more than twice as much. These would really only work well for a motor with some serious hp as they will support over 215hp naturally aspirated using stock fuel pressure and over 205hp forced induction running 58psi fuel pressure.
I now use the 80 lb/hr Siemens Deka 4 injector. They are capable of supporting 260hp, and I don’t think my XB will make it quite that high. They look just like the 60lb/hr injectors but have noticeably larger nozzles: