I'm trying to figure out what is wrong with my 03 evo 8 MR. It is stalling @3000 Rpm WOT 25 Psi, its hopping, cutting in and out. It ran fine at 25-30 psi for 2 years. The AFR is 10:1 when it starts hopping. The wierd part is I can cut it down to 12-15 psi and it runs fine, AFR is correct. There isn't a boost leak. Any ideas?

 

Try a boost leak test and work off the results.

 

how long since you changed your spark plugs?

 

^^ check spark plugs and gap.

 

+1 on checking the gap and throw away the gapper you got from the parts house and use feelers.

 

if you have spark plug blow out or gap issues the AFR will be lean and not in the 10's when its hopping or cutting out.

 

Nope. Spark plug not firing = extra fuel out the exhaust = rich.

 

It's not a misfire. Sparkplugs are brand new. The ecu isn't throwing any codes. It's literally like the engine just rejects the boost and stops for a second during WOT.
And thanks everyone for your input.

 

Sounds like you might be hitting a limiter, do you have the tools to data log?

 

Boost leak test, check all vacuum lines especially the line that runs from the wastegate and the BOV.

 

Pull the plugs and check the ceramic bodies for spark tracking down to the steel body. Under load it will go to ground and cause a big miss.

Fix is to use silicone spark plug boot release on the ceramic ribs, taking care to not get any on where the HT lead connects to the spark plug.

If there is tracking, you can clean it off using a nylon pad. Do this before putting the silicone release materials on the ceramic.

 

Nope, its typically lean. watch the wideband when it sputters or cuts out.

 

Edit

My mistake. Wideband doesn't read raw fuel. I had it backward. LOL

Protip: don't type on forums while concentrating on video games LOL

 

Yes. I can data log, evo scan and easy obdii. It's not throwing any codes. I've checked for boost/vac leak. But it all checked out.

 

what max load are you hitting when you are experiencing cut out?