how to tell....
 

how do u tell if you have an aftermarket MAF sensor or throttle body on a 2001 Z28

Re: how to tell....
 

They look different than stock. Now, if someone modified stock parts (i.e. home port the tb or descreen the maf), you can't tell unless you take it apart and peak inside. Most companies like to put their brand on their products though. If you have a BBK throttle body or an SLP MAF, it'll be obvious.

Re: how to tell....
 

stock on the left...75mm wide...and aftermarket 85mm unit on the right

http://memimage.cardomain.net/member...22_52_full.jpg

here is my ported TB...you can see a smooth transition from the sloped front, to just a flat inner bore. there is typically a lip just in front of the blade (when closed).
http://memimage.cardomain.net/member...2_279_full.jpg

here is a drawing i did on how it helps...it may explain it better

http://memimage.cardomain.net/member...2_280_full.jpg