this motor started acting up last year a little but has become worse. if I throttle it fromm low end to wide open it will not rev over 3000 RPM. If I feather it slowly up it will run normal speed and RPM. I have good fuel pressure rebuilt the fuel pump, replaced the fuel pressure regulator, all filters, and new plugs. The shop I had it at started with the fuel pressure regulator and ended up saying it is droping two cylinders when it is throttled wide open. They claim to have replaced two coils and both CDI boxes, but there is only one new coil and I am positive they did not replace the CDI boxes. So my question is before I buy new ones, does any one think this will fix my problem?
NO, and before you even THINK of buying any NON-returnable electrical parts, you need to do a few simple tests, to determine exactly what is causing the problem.
You need a spark tester, remote starter switch (or a helper), DVA meter (or DVA Adaptor to use with your Volt/Ohm meter), a spark plug wrench.
Download the FREE Ignition Troubleshooting Guide from the Support page of CDIElectronics Their guide will walk you through testing your ignition, wire by wire, even telling you which color wire, etc..
Repost any problems, misunderstandings, and your test results BEFORE buying any electrical parts.
Sounds like you may have a broken trigger wire that looses contact as the throttle is advanced. While testing the trigger, as spelled out in the CDI Guide, disconnect the throttle cable so you can move the throttle from idle to WOT and back, if you lose output during movement you could have a broken wire, PROVE IT.
If you leave all the spark plugs out but plugged into the wires, tape all the spark plug bodies together with a wire attached and ground that wire, this gives the coils a place for the spark to go and relieves cranking load on the starter and battery.