m52 power loss at full throttle

[e-dirtym52]

Well like half throttle it surges when it climbs up in rpms. And anything past half throttle it falls flat on its face. But I do have an extra vanos I got from a friend. Is there any way to tell if it's good or not without it installed?

[dereliiict]

Doesn't sound like Vanos to me. Usually that causes a problem below 5k. It will hesitate and surge during power.

[e-dirtym52]

Any insight would help guys

[e-dirtym52]

It also runs super rich. Backfires like crazy when I let off the gas if that says anything

[e-dirtym52]

So I had issues in the past with losing power but I thought it was because of a somewhat mangled wiring harness. So after swapping harnesses and all that it only throws an evap code because I don't have my charcoal canister hooked up. But it still pretty much falls into a fail safe mode at full throttle. At like half throttle it will almost kick when getting up into rpms. I'm thinkong maybe vanos but I want too sure since it seems to idle fine and all that. So what do you guys think it could be?