I haven't received an e-mail.
Did you use the address in my forum profile?
The first character in it is a lower case L, that might be messing you up.
Anyhow, having any luck with the truck problem?

liftmech I tried to send you a email of thanks. noy having much luck

The injector is "fired" on command by the ECU. The ECU uses input data signals from a few sources (O2 sensor, MAP sensor, tachometer signal) to determine when, and for how long.....the injector is active. The injector will be fired to attain a specific range of O2 voltage and this is a way of leaning out, or enrichening the air/fuel mixture in response to how the outgoing exhaust is affecting the O2 sensor.
If this truck has been neglected (insofar as check light and other parameters) for a while, and now the owner wants it fixed....you could very well be looking at more than a single issue regarding how well the engine performs.
These engines/trucks are notorious for breaking wires near connectors and even chafing the wires inside the main harness against each other to the point of open circuits, or shorting between wires.
If you find any broken wires at various connectors on the engine, Toyota does provide replacement kits for individual connectors, so don't believe it if someone says you have to buy the whole harness.

thanks liftmec no check engine light,bulb gone I guess, is that injector fired all the time or just on start up ?

You also need to confirm that the check engine light in the upper right corner of the dash monitor is lit when the key is turned on, but before the engine is started, and that the light goes out when the engine is running.
If the light is not lit when the key is turned on before starting, the bulb is probably burned out from being lit too long.
None of that about the bulb is going to fix the running problem, but if the truck is having some issues like you describe, I would certainly expect the check engine light to be lit.......and you made no mention of that.
Yes, there is an injector underneath the mixer on this engine.
The injectors do become faulty with age, and mostly plug up with the heavy end byproducts of the LP fuel. I would expect this to be more of a problem if the engine is run most often on gasoline with only intermittent running on LPG.
Cleaning the injectors is usually an exercise in futility.
If you have confirmed that there is no LP being delivered by the injector, replace the injector.
The injector is "fed hot" from the TWC relay but the ECU controls the grounding of the injector via 2 pins on the ECU. The injector is activated by a "non resistor" pin first to assure the injector is activated and then the ground function is handed off to a pin on the ECU that enables the injector to be held in the activated position. This 2 step circuit scheme is to prevent overheating of the injector solenoid. High current to engage the injector with low current to keep it engaged.