ORIGINAL: jthorn9

65mm = stock to lightly moded cars (basic bolt ons)
70mm = mildly moded cars with h/c/i work, and or just head and intake work which requires more flow (also can be used with small 6 psi S/Cs)
75mm = F/I vehicles and or highly moded engines.

Why does the "bigger is better" apply here?....... same principle as with heads selection. Smaller TBs are a "correction factor" for valve events. Get the latter fixed or optimized, and no need for any type of correction (=crutch)...... let it breath to the heads/intake/valve train full potential. Regarding the MAF, it's all in the calibration and transfer curve, BUT you don't want the MAF to become the bottleneck of the intake.

When I put the 90mm TB on RED Death throttle response was much better and it was not as sensiitve as with the 70mm & 75mm. The problem is there is an accelerator pump type function in the EEC and people don't mess with it. Thus when they jam the throttle it "hick ups" and then takes off. The problem is tuning and once again guys want to blame a problem elsewhere.

I agree with yous two but if an average joe goes and slaps a 90mm TB on their mild (if not bone stock) motor without tuning properly, there is a good chance they won't be overly happy with the results, don't ya think?
Not really...... I did an install for a customer that bought a 80mm TB for a '86 SD Auto Mustang. After fixing the TB-to-EGR spacer mismatch problem he created, the car actually "felt" better in terms of throttle response and WOT performance. KIM though, all based on the SOTP dyno, this was a 100% stock setup with the only mods being the TB and new shorty headers. Took care of some EEC problems, and it was better (driveability wise) + the famous "torque down low" was not lost..... + it was now able to spin the tires from a standstill. The grin on the customer's face?..... priceless.

What I mean to say is, you could install a bigger TB, but if all the other details take a backseat in importance...... you will create problems that are wrongly attributed to the bigger TB.

While obviously the TB cannot be bigger than the intake opening, but a TB + MAF meter cannot be too big. Air speed is NO CONCERN here as it is with a carburetor. If a person is compitent enough to buy parts, then compitent enough to have them installed, then they had better be compitent enough to tune the damn thing. If they are NOT that compitent, then THEY are the issue and not a piece of aluminum.

I can get further into this if needed, but so far the entire thread sums up what most people actually understand about EFI, which is not much.