Beginning about the time I put on the UDP, I noticed a power loss in the upper rpm band. You can see from my dynos - I lost 13 whp after addition of the UDP.

Finally got a chance to test it at the track.

I have previously consistently run sub 15s with crappy 60' times at about 95-96 mph.

Saturday at the track, the best I ran WITH A 2.194 60' time - was 15.06 at 91mph. Pitiful. With a 2.194, I shoulda been at least 14.7. Trap speed shoulda been around 95-96. SO. . .

I TOOK OFF THE UDP on Sunday. Guess what - I still have the same problem. Car feels flat from about 5800-redline. So, something else is the culprit - I think.

Mechanic suggested the fuel filter - but it is in the trunk and supposed to be maint. free.

I previously had a problem with stalling/wanting to stall after hard acceleration followed by clutching and braking. I thought I had fixed it when I took off my intake and cleaned the filter, since it seemed to disappear. But after resetting my ECU last night - its baaack. I'm thinking its related.

So far, the only things I can think of are:
faulty intake runner changeover - see my dyno below - power falls off beginning at intake runner changeover.

fuel filter

the non-nissan gas cap I have

02 Sensor

anyone have any guesses? I'm going to redyno to confirm

Any ECU codes?

I'm not farmilar with the 5th gen fuel filter set up, but it does sound like a fuel dilevery problem. I doubt the intake runner would cause the car to stall, it would just rob you of power.

I doubt the gas cap would matter, and if it was a sensor you'd have the MIL on.

Ummm, not positive on the 5th Gens, but on the 4th Gens the fuel filter isn't in the trunk??? Are you sure about this?? I mean we do have the same engine so I figured it would be in around about the same place?? And I know my fuel filter isn't maintenance free either?? Sorry, just got confused lol

Oh, and how many miles has this been happening?? If not many then maybe bad gas?? Also might want to check your plugs??

Might be the intake runners not switching over like you mentioned though... not sure how to trouble shoot that??

I agree... but it could be a cobination of two problems??

Yep.. doesn't sound like a sensor problem.

The fuel PUMP is in the trunk, well in the fuel tank actually. The filter is in the engine bay.

I think 5th gens have an inline filter near the tank. I don't think they have one in the engine bay. IIRC it is a maintenance free item as well.

How many miles you have? The fuel filter is old/dirty/clogged can rob you of some power. It can make for lower than expected performance at higher speeds too which may be the case. It is ten bucks to do this. Try swapping it out to see how it goes for you.

SuDZ

I'm not a 5th gen owner, so excuse this if it's off. When you changed out the UDP, did you by chance mess with any of the ignition or cam timing? Are you perhaps getting ping/detonation/knock? Sounds like detonation, but you would've noticed that on the dyno. Some problem with variable-intake/valve-timing, or ignition/cam timing would really be able to affect you on the top end, fuel filter would hold you back all over.

From what i've been told, the fuel filter is somewhere near the pump (supposedly maint free).. in a 5th gen, you need to take out the rear seat to get to it... (there was a tutorial somewhere on the web)

-Tom Z.