Quote Originally Posted by BlackW1dow View Post
Good news, I was able to tune out the EGR and code 26 from my 92 vette. now i have another question. What all do the companies change when they say they can send a custom chip to gain 10-15HP? how do they do that without datalogging?

after i datalog what are my first steps to tune? is the ultimate goal to get the BLM to 128? Theres soo many scalers and tables that are able to be changed but i would think a sorta simple tune would only require changing a few things like VE tables, Spark Advance, and fan temp turnon.

Thank you greatly for the help on finding the right XDF.
Woohoo! Glad to hear you're sorted. Yeah, the XDFs available directly from TunerPro are woefully out of date compared to those created by the community here.

Anyway, the "magic sauce" that legitimate companies (like pcmforless) charge for are tweaks to ignition timing and fuel maps based on their experience with others who have had similar work done in the past. Since they have experience with several similar vehicles, they can create an "average" improvement that should work for any other similar vehicle. It won't be as nice as a tune with proper datalogging, but if your vehicle falls within the specifications of one that the company has experience with, you should still be able to see some improvement.

Hypertech is not a legitimate company, so just ignore them.

Tuning on these older ECMs is a little more involved than newer ones, and I don't have direct experience with your ECM specifically, so I can't walk you through every single step. But in general, you'd want to adjust fuel to get the BLMs to 128, yes. If you feel spicy you can then start tweaking ignition timing, but you'll want to be sure to keep track of knock counts and all that. There'll be a falloff point where adding timing doesn't actually net you a benefit, not to mention it'll make you more prone to knock, so start slow.

Hopefully some others with more experience with the '278 can chime in here. For general tuning-related stuff though, plenty of folks around here should be able to help, and there are entire online courses that are applicable to all engines (though the actual nitty-gritty of how to log the data, make adjustments, and apply them to your specific ECM are not covered). Good luck, have fun!