I wouldn't pack it in so easily or quickly, just need to work smart and not throw needless dollars at what you think may be the problem. I think my old auto shop teacher used to teach us that an engine is nothing more than the following: Intake, Compression, Power, Exhaust. Intake is air/fuel, compression is self explanatory, power is spark to the compressed air/fuel mixture at the correct time, and then burnt gases out the exhaust. I'm not the best mechanic(no kidding)but I do know where to start, the basics. Any of the big four out of whack and your Yota is running like crap. Check the compression, check the timing, make sure the spark plug wires are routed correctly, pull the
codes, check for cracked vacuum lines, check your ground wires, check your connections. Who knows, you may need to pull out the voltmeter and the FSM and start checking MAF meter, TPS, or any number of different items.
My point, keep at it, use the search function on the forum, ask questions when you don't have the answer.
Good Luck