2001 RS4 with recently fitted MTM 337kw kit loses boost after simultaneous starts (say 3 or 4 times but is somewhat random). Can scan engine and clear fault codes and boost comes back on.
The fault codes are "Lean on both banks". Checked exhaust AFR with independant meter which showed 14.5 on idle and between 14.4 and 15.3 on full boost. Does anyone know what the expected AFR should be on this MTM kit or if anything else could be causing the loss of boost. I'm speed deprived!!!!

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RAG

Try checking for vacum leaks. I had both banks running lean in my 2.7T cleared codes performance came back. does your car have trouble starting in the cold sometimes?

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Have cleared codes and boost comes bank.... till next time I drive in traffic and stop/start approx 3 times.....then back to limp mode.
No problems starting.
AFR ratio is 14.5 to 15.3 under boost.
Error codes still "Lean on both banks"

Driving me nuts (wish it were boosting me nuts)

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RAG

Sounds like a vacuum leak. check the line to your fuel trim bank. on the left side on the engine bay under your top left engine cover. my line is torn but cars performance is still okay.

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14.5 at idle sounds good but 14.4 to 15.3 on boost sounds a little high but I may be wrong.

that seems way to lean to be at 14.4 on boost. at idle you want to be at 14.7 boost around 11.5. at least thats what im going for on my car

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CLX- it's better to have it and not need it, than need it and not have it.
Preparedness is not paranoia.
"A turbo: Exhaust gasses go into the turbocharger and spin it, witchcraft happens and you go faster." Jeremy Clarkson