Hi guys,
I don't know if i am in the right section, if not please moderators let me know and will gladly move along.

Yeah gas right... tell me about it! Let me start by:

*I had a System Charging issue on my Vette before the Meth kit. Causing the car to stall and run rich.

-Had my SC belts changed (TVS2300)
-Had the belt changed
-GM ignition wire set (MSD's causing misfire under load)
-Swapped GM alternator causing DIAG ELECTRICAL ISSUES for a MECHMAN high amp alternator 170v
-Last step was the ALKY kit
-Dyno tune (by a very reputable shop)

-MY SET UP
-LS2
-M6
-STOCK CLUTCH
-STOCK BOTTOM END
-STOCK TRANNY
-Cam (mild)
-Headers
-Xpipe
-CAI
-TVS2300 SC
-MSD FUEL BOOSTER

Having electrical issues with the Charging System was a PIA causing the car to run rich and that annoying beeping sound come on every 5 minutes it was just nerve wrecking. Took my car over to (reputable shop) and had it diagnosed and came out with the solution of swapping the GM alternator which i had just replaced along with the battery 5 months ago for a MECHMAN 170v....IT WORKED! No more beeping crap at the very least. After the alternator they moved along to replacing the supercharger belt since the old one had a rip on it (never slipped). Finally before the ALKY KIT they changed spark plugs and recommend e to change to OEM GM cables since the MSD ones that i had cause issues with misfire under load. Dyno Tune came along and even though i requested a before baseline run on the Dyno to see where i am standing before pulling the METH numbers it was never done, not sure why they choose not to even though they requested $100 extra for a baseline and agreeing on it.
A month went by (alternator was in back order) car was ready Picked up the car and drove it home (14 miles) and notice high coolant temp 225 at 45MPH and occasionally it would stall and also notice that on a FULL TANK i was ranging 174 miles with an Average consumption of 8.8 MPH!!!

Call them and let them know of such issues and that in my humble opinion it was a calibration tune related problem. Took it back the next day and they told me it was because a bad wire connected on the SC that was causing that and that there was no need to Dyno the car again. TODAY 8/17/18 Picked up the car again and the car was running much smoother even though it was very hot out there (92 FL) i was getting Coolant Temps of 205 A/C on stuck on traffic and it will drop to 199/200 as soon as started moving...BUT,,, once i started switching to the MPG I notice that on a FULL TANK i was ranging 174 miles with an Average consumption of 8.8 MPH!!! AGAIN!

My question to you guys is this normal? Should i see that much gas consumption with such mods? I was getting 28MPG before the Meth kit.

Attached are the pics of my dashboard were you can see the MPG and a FULL TANK picture @174mpg, ignore the Check Engine light since that turned on as soon as i took my car from the mechanic shop the first time right now it has been corrected. Also if you guys would like to chime in about the Dyno numbers for such mods it would be greatly appreciated.

THANK YOU!

 

Any car with aftermarket injectors means that is going to be WAY off. You need to actually measure at the pump.

 

Exactly...have you even driven it to see if the mileage is that bad? Other possibility is what they did to tune the meth. If they pulled a bunch of airflow out of the maf table rather than PE it may skew the mpg reading as well.

 

I'll fill it up again and check how many (MPG) i get yet as of today i only drove the car about 50 miles and my tank is at half way... and that is driving on stop and go no WOT in any way.
Injectors are the ones that came with the Maggie.

 

following

 

Interesting. IDC is thus irrelevant with E40 or E38 PCM?

 

You're right, on second thought screwing with the maf curve wouldn't throw the mileage off but it's still the wrong way to do it, especially for an A6 as the airflow model needs to be correct.

The mileage readout depends on the correct injector data but even with the right data the readout will be incorrect if they scaled the tune to handle the additional fuel/airflow. Newer e38's typically don't need to be scaled but the older ones do. I'm running ID1050x's and my mileage readout is correct on my 2010.