It can depend upon what you are doing. What size MAF you have now? What are you building cubic inch wise? If you only have a stock meter or small aftermarket and you are building a 347 or something with your KB on top, you might want to upgrade to an 80mm or 90mm MAF with the proper calibration for your 42s...
If the MAF you have now will measure the total flow the engine will see, it can be kept (in other words if it is not pegging the voltage at WOT and redline). If not it may be able to be reprogrammed.
If you do not get a MAF for 42's the car will likely not run until it has a tune. If it runs it will be pig rich. Even with a MAF for 42s the engine should be tuned or checked out because of the KB. Plus low speed/idle with 42s is usually crappy without a tune.
I currently have a Pro-M 75mm MAF that's setup for the 30lb injectors. I plan on getting the car over to a dyno to have the diablo-sport chip that's in the computer retuned once I have the motor reinstalled. I first have to figure out what I'm doing about the motor.
Seems like it's not much extra to do a 327 or 342 over a 306. I know I'd need more fuel if I go bigger, so I'm trying to see what that would cost in terms of the fuel system upgrade.
Dan sell the 30# meter along with the injectors and buy a larger meter (80-90mm) to go with the 42's. You will run out of headroom on the 30# meter if you just change the chip so it works with the 42's.
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