Help needed with my GTI :(

[vwvwvGTI]

Having serious problems with my MK4 Golf GTI 2.0i


The car drives great except now if I try to "floor it" when overtaking etc, it seems to loose power and stutters, yet if I accelerate slowly it runs perfect!

the loss of power (engine stuttering) really worries me. also if I rev it it sounds as though there is a hole in the exhaust, but I have had it up on a lift and couldnt see any!?!

I used the VAG-COM cable and soft and my car read back...

16806 - Main Catalyst: Bank 1 : Efficiency Below Threshold 
P0422 - 35-00

can anyone tell me what would cause this stuttering? and if there was a hole somewhere in the exhaust system, such as the manifold, would it cause this loss of power affect?

any help or advice would be great !

Thanks in advance!

[oliver07]

start your car put your hand over the tail pipe if the car is close to stalling no hole if it ticks over as normal hole as the gasses are escaping

[vwvwvGTI]

Good Morning Oliver,
Thanks for the info I just tried it and the car stalled, so im guessing its no holes in the pipe?

Any other ideas? 

[oliver07]

vag com
as i would have said
maff
dirty throttle body
coil pack
plugs

[TJJONESVDUB]

i would say MAF & plugs myself

[vwvwvGTI]

Firt off let me thank you for trying to help! I posted so many times and with no reply 

second, Could the MAF really cause the loss of power, and by this do you mean the MAF sensor?

I also wondering could anyone illustrate with pics or diagram, where the following are located? plz?

> dirty throttle body
> coil pack

[oliver07]

mate use the search section or the maintanance section under mk4 the coil pack is the part that fits over the spark plug you will have 4 of these check to see if its fully pushed down or look for any cracks in the unit.
if the maff is dirty it will give poor running as said follow the links and give it a good clean

[Rhyso]

Pretty sure the 2.0 only has an ignition coil and not seperate coil packs

[oliver07]

glad your on to share your knowledge on this.
 I have the gti T had a few running issues so just putting ideas forward.

[Rhyso]

glad your on to share your knowledge on this.
 I have the gti T had a few running issues so just putting ideas forward.

sadly my knowledge is limited - wrong fuel lol

I'd say you're on the right lines though    Only thing i would say is with regards to the cleaning the MAF you can over clean it and therefore finish it off quicker