I installed 45lb injectors on my 99 ls1. Do I need to upgrade my fuel pump? I was told using 45lb injectors would cause my car to lean out at full throttle ( I don't know how , but, that's why I'm asking) If I do what the cheapest (best) pump or bosster pump?

 

I'm assuming you retuned the computer to correctly control the injectors. In this situation the computer will administer fuel based on the engine power requirements. At this point, the pump only has to supply fuel to support your needed power & larger injectors will only effect the pump if they are trying to flow more than the pump is capable of.

Based on this, both the injector size & pump size are directly related to your power level. Now if you were truely exceeding the limits of stock injectors, you stock pump is probably marginal as well. Although the stock pump is decent, I would probably consider upgrading somewhere around 400rwhp or if you have a lot of miles on the stock one.