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The farther away from mainstream you go, the more likely your tune will need some tweaking.
The bigger issue is the injectors that are now getting more common in the Z32 market.
The 740cc injectors that were manufactured as 740cc injector are pretty close from car to car. These are Nismo, Blitz, Tomei, HKS. Basically all made by the same company.
The stock 370cc injectors from Nissan are very stable as well. The early 555cc were also good before ethanol was introduced and started killing them.
The Sard 850cc injectors are also fairly close.
Where you get into a huge can of worms, is going outside of the injectors above.....
The DW, Jecs, Venom, ect.. injectors being sold (some new and some used/rebuilt) started out as smaller injectors (At least all the side feeds). These are all bored out injectors that were smaller. These injectors flow very different at various open times, and each set can be very different from the next set.
Some of these injectors can not be correctly tuned at all! Other require a lot of work to get reasonable.
You can not make canned tunes for these injectors based from the math, the flow rates are not consistent, and the likelihood they all flow well at every RPM level is questionable at best. They have drilled out plates that are typically extremely crude.
The problem is they tend to dribble fuel rather than spray.
When you get into top feed injectors, how many cars have been tuned with the injector size you use with top feed injectors? If they tuned only one car with that size, was something wrong with that car that makes the program funky? Did they guess at the program or just give you a program based on math for a side feed program?
Different brand injectors of the same size flow differently and require different programming. The change to side feed will be another complete program to be correct.
Most K value and L Values are not set exactly what the math would be.....The original programming was designed for fuels that we do not have today. The ethanol in today's fuel requires higher than normal numbers for the cars to run correctly, this is because these fuels add oxygen and need more fuel in the program for a proper burn. It is common for MAF's that are now 20 years old to read slightly different from one another, also adding to why you really should custom tune all of these cars.
If your right on the edge of being too lean to run well, one MAF that reads just slightly less will cause more issues.
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