I have Toyota motorhome 1991 v6 engine 20k miles rebuild by Toyota in 2012 .The engine running rough at idle hot or cold. At cold the power is not good. Some times ' i have code 25 and 26.Injectors was clean by dealer when they rebuild the engine. No vacuum leak , clean throttle body ,replace the afm by used one. Same problem. Anyone can help me Sorry for my English i am french.

 

Help us help you.. We don't have trouble codes memorized, and you've already looked them up or been told what the codes refer to?

25-26 are AFR lean and rich?

Have you check for exhaust leaks? (Sensor needs a reliable exhaust flow)
Tested the oxygen sensor signal? (Loose connectors are bad)
Replaced the oxygen sensor recently or when the engine was serviced? (What is the service interval on an o2 sensor, from memory its 30k)
Has the vehicle sat for extended amounts of time? (Gasoline has a shelf life based on climate, after a certain time it starts to varnish which gums up lines, filters and injectors)
Did you test the old VAFM and compare it against the new one? (Part swapping is bad! Don't guess a part is good or bad based on a whim. Test all parts versus the published specifications. Parts that were working don't magically fail, and new parts don't always perform as expected..)

You cleaned the throttle body? Did you check things like the throttle plate resting position or the shaft play? How certain are you you got the gasket sealed, or the linkage adjustment correct? (There are engines currently running that have "driven to the moon and back" and never had the throttle body cleaned. Does this have an effect on the flow volume, yeah sure but not enough most people are going to notice.. This biggest effect of a grungy dirty carbon caked intake plenum is a delayed reading on the EGR temp sensor which will trigger a warning light but have no real effect on the ECU performance.)

..
Check your ignition timing.
Resistance check your high-tension cables (sparkplug and coil primary leads).
Efi tune-up (this is pretty much changing the sparkplug set. So much nicer than setting gap on ignition points and tweaking carburetor jets and mixtures etc..)
Inspect the signal wire for the ignition system (NE signal from distributor for cracks in the insulation. They used the same wire supplier on the 22re and its prone to degradation after thirty years of soaking in engine bay heat..)

..PS one of the 3vz guys will be along shortly, maybe, and give some more specific tests hopefully.