sounds like it could be related to the N75 vavle or a boost leak. Maybe even your cat has a crack in it? It may be the turbo though. I would take a look at the lines. Also try and get access to a VAG.

I have heard ctsturbo sells some faulty turbos, but i would do some searching around the forums on here about them.

"which is better: k04 or GT25R?"

Well...that is sort of a personal preference thing. K04 will have better power down low, especially with the more aggressive tuning. What year is your B5?

GT25R will have more lag, not like the GT28R or GT28RS or GT2871R like what most guys are running out there for BT set ups. But it will have more lag than the K04, although it has the ability to produce more power, the powerband will be more up top compared to the k04.

Depends on what kind of software you get with the GT25R also, i dont know any software for that turbo, my best guess would be a custom tune.

IIRC, the GT25R is a GT2X eliminator from ATPturbo.com. GT2X is not the real garret GT25R, it is a little different but pretty close to the same. There is a guy on AZ running the GT2X and the PC16(k04 software for a 97-99.5 B5) and he just ran a high 13s 1/4 mile. Dont recall his trap speed or 60 foot time, but he was running a stock cat and stock IC.

What i would do is get the GTRS kit from Renn-art.com. The kit is running for $2800 on a group buy, that is a steal if you ask me. Check out renn-art.com and they have the products listed that comes in the kit. It will produce some very big numbers and lots of power.

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