I have noticed lately my car isnt as strong. Looking at old data logs I can see its not breathing like it used to. Before installing LE heads and switching to LT headers I dynoed the numbers in my sig. After the install the car felt a lot stronger and when I hooked up datamaster I noticed it was pulling around 40 gps more air than before. Recently however its never more than 30 and only in a few areas of the chart. What do you guys think is the deal here? The tunes are nearly identical btw before the heads, after and now... I am at a loss.

 

How much air are you flowing? Since the MAF measures air mass, colder temperatures lead to denser air and higher readings. Did you install the heads and headers during the winter? Your MAF readings will be lower in the summer versus the winter.

My car pulls 350-360 when it's cool out. On a cold day I have seen as high as 380. During the summer, I usually peak at around 330.

 

The higher readings were during winter so maybe thats the problem. The motor doesnt use any oil and I run 0w40 M1... no cats. For some reason they MAF only peaks around 318 now which is pretty low considering the ported heads/cam.

 

318 is pretty low for a H/C setup. Have you re-oiled your K&N since you got higher readings. It's really easy for the oil from the cotton filters to contaminate the MAF and reduce your readings. Take some brake cleaner and spray your MAF wires with it. Then dip a Q-tip in brake cleaner and GENTLY wipe the wires and resistors.

I was dyno tuning a H/C 383 car and he had similar low MAF readings and was running lean. We swapped his MAF out and he jumped from the 320s to the 360s. If this is happening to you, you would also be running lean and that could be part of your power loss.