High RPM miss/hesitation

[11lariat]

Hey guys..got a question for ya, someone's gotta know this..

Since I bought my X in January, it's had a miss/hesitation above 4,000 RPM.. I tried the standard fare of replace the air filter, clean the MAF, check for vacuum leaks, etc. It was also suggested to me that it could be the vacuum modulator on the tranny, so I pulled the vacuum hose..and, as i expected, it was clean. I'm running out of ideas. I've run countless bottles of fuel injector cleaner, put Marvel Mystery Oil in about 100mi before an oil change (didnt help this problem but quieted my lifters a bit). It's got new Bosch Platinum +4 plugs and Bosch wires, same as my dad's '92. I think it's been getting progressively worse.. I like my X, but I'm getting really frustrated with it..any suggestions you guys have would be greatly appreciated..

Thanks.

 

[11lariat]

I also forgot to mention, but I'm assuming it's related...

during an upshift at WOT, there's a fairly loud "clunk" coming from what seems to be the passenger side of the vehicle, but I haven't been able to findo ut much more than that because I usually drive alone..any ideas?

Thanks again

 

[marragtop]

Have you cleaned or replaced the IAC? Also, have you pulled the codes to see if they reveal anything (maybe the throttle position sensor)?

 

[11lariat]

I haven't cleaned the IAC yet, I'm planning on doing that this weekend, as well as replacing the fuel filter..unfortunately i don't have access to a diagnostic computer right now or i'd check for codes as well