Maybe, but i def noticed a "lag" in low end after my g3 install. But after a few days it seemed to pick right up. Maybe it was just me. Either way, the pros out weigh the cons for both mods.

Every car is going to studder if you do a mass of mods all at the same time and the ecu doesnt have time to adjust. If you do em 1 by 1 and even have even a week between em, your car will transition smoothly. Then you get to a point like me where I had all bolts ons and no tune and the car ran ridiculously rich as the computer could no longer compensate enough lol.

Also, you have to take in to account this key question: Are you talking about Open or Closed loop?

I would think that in Closed loop, at low RPM you'd probably be fine because the sample rate of the MAF/O2 is high enough that the ECU can adjust, but at high RPM it may fall a little flat until learned data is adjusted.

In open loop, I could perhaps see a few % drop at very low RPM (sub 3000RPM) until the learned data is updated, but you'll definitely have measurable gains above ~3K or so because it's at those RPMs and higher that these aftermarket parts' higher flow and lower resistance actually makes a difference, tuning deficiency or not.

There's tons of exceptions depending on what parts you pick and how they were designed, but for this guy, he's not gonna see any meaningful drop off in power or torque except perhaps immediately off idle. Which doesn't matter, really.

If the OP is worried about it, just cruise one gear lower for the first day or two until the ECU has time to learn, and do a few WOT pulls in 2nd and 3rd gear so that it can get some good data to learn from. Start @ 2K RPM in 2nd and hammer it to redline, upshift, slow to 2K again in 3rd and hammer it to as high as you feel comfortable on the highway.

This will put enough load on the engine that the ECU can gather meaningful fuel deltas to adjust the learned compensation data.

/endnerdgasm.

Edit: and for the unintiated, Open Loop is wide open throttle, Closed is part throttle (aka, normal driving).

The car uses the MAF tables and learned fuel compensation data to determine fueling in Open Loop because engine RPM is generally changing too fast to compute the deltas real time using the MAF and O2 readings. This is due to mechanical and electrical latencies. This is done in pretty much every car on the market because the O2 sensor is the real limiting factor, being that it isn't inside the combustion chamber and the element that does the measuring doesn't react in nanoseconds or anything.

What If i only install Stillen Gen 3 intakes and Fast intentions cbe. Will i loose low end hp and torque for high end?

Well, technically Open Loop is "control based on static tables + learned trim values" and Closed Loop is "control based on sensor feedback directly". You can have Open Loop without full throttle. Normally only during initial engine warmup, but also if you screw with your ECU settings too much it can stay open full time because it never sees the right conditions to enter Closed (I had that: from putting the idle high and adding fuel at the bottom of the rev+pedal range. Car drove great, but never-ever entered Closed Loop. Didn't even notice until I needed to get it to pass an OBD-II inspection and it would never complete a Drive Cycle).

Back on the original question: Gen3+HFC+CBE shouldn't really hurt you anywhere in the rev range once the ECU adjusts. LTHs do hurt the very bottom end of the rev range, sub-3K. It'll get a little laggy digging out of that hole in high gear, but it's not a huge thing. There's really no reason to care about sub-3K performance anways. If you want the car to do interesting things, downshift more :)

Everything this man said is correct.

I was dumbing it down to how the ECU behaves with stock tables after warm up cycle. It's absolutely true you can go into Open Loop without going WOT, but it's usually @ fairly high throttle openings or if there's something wrong.