ever heard of this engine problem?

Yesterday my engine started doing something rather bizarre. Regardless of what gear I'm in (5-speed manual transmission), the engine won't rev beyond about 4000 rpm. Once I hit 4k the engine shutters badly and holds that rpm as long as I keep the throttle buried. If I didn't know better I'd say there was a rev limiter. I've never had this happen before, and I've run it to redline on many occasions. Any ideas? Many thanks in advance for your help.
p.s.  I don't know if this is related or not, but my speedometer went wacko just before the engine problem appeared.  The speedo jumps all over the place and hasn't returned to normal since then. 

sounds like the ECU is telling the engine to cut out. It definetly isnt a rev limiter because that higher. I dont know what would go wrong to cause that

Definitely electronic.

maybe you should start by telling us WHAT YOU'RE DRIVING.

my apologies... 1999 Mitsu Eclipse GS-T 2.0L turbo.  I just tried to pull codes from the computer, but there weren't any.  Speed sensor???

check for ruptured or disconnected intercooler piping..  Specifically at the top of the intercooler (have seen them break there).

intercooler is intact, along with the tubing

when you have it in neutral can you rev it past 4k??? if so you aren't producing as much boost when you are in neutral so you should be able to rev it as high as you want if it is a boost leak.   let us know if you can do that.

in neutral it'll rev all the way up.  does this mean I have a problem with the turbo's waste gate?  how do I find this suspected boost leak?  and in the event that I'm not accurately describing the problem, the engine shutters in order to drop back to 4k rmp or to keep it from passing 4k - sometimes it will rev beyond 4k but then the engine does it's wierd thing to come back to 4k.

battery load tested good.  funny thing, though.  during my trip to the auto parts store, a few times I could rev as high as I wanted without problem, other times the engine "cut-back" again a 5500rpm and 5k rpm.  

if you can rev it as high as you want in neutral but you are cutting out around 4k than it sounds like a boost leak.  check all of your couplers, piping, intercooler.    if you can't see or find anything than you will have to use or make a boost leak tester (2 pieces of pvc pipe, 90 degree bend, cap and compressor tap.) and test it that way.

I noticed something else that may be of use.  Without a load on the engine (in neutral) there is no problem revving the engine.  However, with a load (in gear) the engine cuts back in the 4k to 5500 rpm range.  What's interesting, though, is that this anomoly happens even when the turbocharger is not engaged any more than just cruising down the road at 55 and not accelerating.  What I did was left it in first gear and when I hit 3500 I just accelerated, ever so slowly, up to 4k so that the turbo wasn't increasing boost.  It took about a minute for the acceleration and was ever so slight that it would seem to indicate that it is not related to the turbo, else it should happen at any rpm where the boost reaches a certain level.  Does this seem logical to you, or am I off base here?

i duno dude... i still say it sounds like a boost leak but that wouldn't make since if the turbo wasn't spooling when u were accelerating than that would count that problem out.

Found the problem and it was an easy fix.  The electrical connector was not securely attached to the vehicle speed sensor on top of the transmission.  Once locked down, the speedo started working properly again and the engine doesn't miss a beat.  Go figure...