I have a 2000 Audi A4 Quattro, 1.8T.

I’m new to turbos and am trying to find out why under mid acceleration, I peak anywhere from 15-20psi and then completely lose it. Boost leak perhaps? I’ve done so much research to attempt to figure out what’s happening but with so many threads & sites browsed, im getting lost in the sauce and thought i’d reach out for a hand!

Some notable mods are it’s F4 K04 Frankenturbo, Turbosmart boost controller. Has a forge diverter valve aswell & Unitronic stage 2 tune.

Boost controller is set at 20PSI. This has been the target amount. The issue is that it had a hard time holding it. Perhaps too much?

If i were to explain it, (and i’ll try to link the vid of it occuring) every time i accelerate hard, it will build up to anywhere from 10-20psi, and then immediately lose it back to 0, continuing to build up again. Sometimes this fluctuation happens two to three times before it manages to hold 20psi until I let off the throttle. Very rarely does it hold 20psi the first time without any fluctuation.

It’s worth noting that the exhaust manifold, which usually is held with 3 bolts, currently has 2 as the previous owner snapped one. It is secure, but Is it possible that the 2 bolts are not creating as strong of a “seal” for air, causing it to leak which would explain why i’m losing boost? Noob question.

I’ve checked over all the hoses and none appear to be cracked or loose. I’ve tightened every clamp I could see. Still, it occurs.

Any help would be appreciated.