"This is the Granatelli MAF Upgrade for the S-10 4.3 V6 Vortec motors. The upgrade is a new thermoplastic front and rear housing and modified MAF sensor. The new pieces are larger in diameter and will not absorb heat like the factory aluminum housing. The factory MAF had 7 preset timing curves, the Granatelli only contains the top 3 curves assuring you the best performance. This upgrade adds 15 rear wheel HP, 9 ft/lbs torque and should reduce your 1/4 mile ET by about .15 - .20 seconds. Installation was straight forward and took about 20 minutes. I had to get a 3" pipe adapter to connect my AIRAID intake kit to the larger MAF housing which cost $4. The cheapest place to pick one up is Summit Racing.
NOTE: MAF sensors are very delicate and you should take extreme care when installing one."
That sounds like a direct copy and paste from Granatelli, I haven't seen a person on here that has actually had something positive to say about it, stock is good for 275hp anyways so why bother? $250 bucks will get you plenty of good mods, roller rockers, intake, exhaust, shift kit, etc.