what are some of items that can it be faulty even though its not visually leaking?

The rubber seal that pushes the fluid though could be faulty and not allow any external leaks. (my guess)

so in essence, it leaking inside the container? Short of replacing the cylinder, I wonder how one can verify this?

if u are running aftermarket pads/rotors the brakes are not going to bite as hard as stock. My bone stock brakes had neck snapping power, as soon as u changed the lines/pads/rotors all that went away. The brake pedal should be more progressive and not have the "ON/OFF" switch like the stocks do.

If that is not the case then, like others said, there might be some air left in the lines when the brakes were being bleeded.

http://www.babcox.com/editorial/tr/tr502b.htm

Not sure. I doubt most would actually take it out and inspect it. Most likely just replace and see. At least it's not too expensive

i agree Vlad on the "bite", but that's diff than soft. I'm thinking the master cylinder might be a good place to start.

That generally gives u the sensation of the brakes not working properly especially if u are used to that "bite".

OP should stand on his brakes and see if the pedal slowly goes down. Ala the article I posted. Takes 3 sec to check and it's free.

I've bleed the system the proper way to get the air out of the ABS unit (all you need to do is unplug the battery). I've since upgraded to a 4 corner BBK and still have the soft pedal feel. One thing I have noticed is when I put the racing pad on the pedal firms up a tad and seems reasonable.

Has anyone tried this?
http://www.grubbsperformance.com/servlet/Detail?no=2635

A soft brake pedal can be caused by boiling the brake fluid while on the track or the pads becoming too worn - requiring more pedal travel to engage the pads on the rotors. You said the pedal firms up (better feel) when you installed the race pads. The race pads are probably thicker than the previous ones you were running, which would account for the firmer feel.

I was going to suggest stainless steel brake lines, synthetic brake fluid and bleeding the brakes at the end of each day at the road course, but it sounds like you've done all this. Did you check the fluid level in the brake master cylinder? Also, properly bedding in new brake pads is very important to ensure proper performance on the track, otherwise they won't grip as expected. Good luck - hope you find a solution.

I have this exact issue with my brakes. I thought I was crazy, but this is exactly the problem I have. One pump kind soft or spongy, second quick pump and nice firm pedal.

I have an 04 coupe, stock pads and rotors, noticed this ever since I bought her a year ago. I have since switched rotors and pads to aftermarket, I DO NOT RACE ON A TRACK, this is strictly a daily driver... I have not bled the brakes, I was considering having it done by a shop...but now I don’t want to waste the money as it seems many have done this with no change.

I just changed my rear pads and rotors and I did notice my drivers rotor was worn more than my passenger side rotor. Leading me to believe I may have a faulty passenger caliper or leak, which may cause this issue... I am going to check this out but will be following this thread with great interest.

I "Googled" Infiniti G35 Brake Master Cylinder - and found this interesting thread that pertains to 2003 and 2004 G35s, which may explain what you're experiencing.

Nope, I still have the soft pedal issue with all new pads and rotors.....but that is an interesting article, thanks for the find!

guys, im having the same issue after I replaced the two front rotors and brake pads last night. Bled all 4 a few times but still getting the soft pedal.

I tried something similar on my '92 300ZX that had a soft brake pedal, and it made little to no noticeable difference. You'd have to have a pretty decent amount of firewall flex to have your master cylinder move that much. I think this is more hype than anything, though some claimed it made an improvement. Either way, $145 for a bracket and a bolt is crazy and I don't think it would solve your problem.