Your repair advice, please?

I have a '99 Toyota 4Runner SR5, 2WD, with ~250,000 miles on it. The engine is a 5VZ-FE, 3.4 L, V-6, automatic transmission.

Lately I'm having intermittent problems with rough idle, usually while waiting at a stoplight, sometimes also while getting up to speed on surface streets (I'm avoiding freeways). When the rough idle happens, the check engine light sometimes flashes, otherwise it just stays on. But yesterday, for example, the car drove fine all day - no rough idle, no flashing CEL. I suspect maybe weather has something to do with it - it seems to have problems on warmer days but runs fine on cooler days?

I took it to a shop that I trust, and they pulled codes
P0171
P300
P303
P306

First they replaced a coil, but that made no difference at all. They were kind enough to put my old coil back in and refund my money.

After further testing, they now recommend replacing the #3 injector, plenum gasket, and mass air flow meter.

Question: Does this sound about right? (Plugs, wires and 02 Sensor were replaced 3 years ago...)

Problem is, I really can't afford it. If I can wait 4 months, I *think* my state will help with the repairs through its clean air program to get the vehicle to pass emissions inspection. (Does anyone have experience with Air Check Texas? Would these repairs likely qualify?)

Also: How long can I put off these repairs? What's the worse that can happen if I continue to drive it ~1,500 miles over the next 4 months? (I only drive on road, and gently at that...)

 

Have the Catalytic converters ever been replaced? Have you changed the fuel filter lately? Clean the maf, change the fuel filter. Is it hard to start first thing in the morning after sitting all night? if it is, Fuel pump might be going away. Never heard of clean air thing, where I am Bell County, they don't do emissions testing.

 

You may need new injectors in the #3 &#6 Cylinders. Warm engine/injector can cause the spring to stick in the injector. I had the same on the #1 Cyl and a new injector fixed the problem. Codes were P0300 & P0301.