Esp8266 TX and Arduino RX need a transistor ?

Ok i never used a transistor, and it works, but lots of time i see strange chars in serial output. Specially after +IPD,9hSTRANGECHARS and after >Sending len:9<CR>STRANGECHARS

I use:
SoftwareSerial serialEsp(2, 3);
serialEsp.begin(9600);
Serial.begin(115200);

I've tried also to down serial to 57600 and 38400 but nothing change.

Pheraps it can depend from voltage ? pheraps need transistor on Esp Tx like the guide??

For Arduino TX to down for Esp RX I've used a 10k and a 22k resistor...(2k of difference can create problems?)

Thanks a lot for everyone can help me, but i can't understand why esp work very bad when i add to my sketch Esp8266EasyIoTMsg function and esp.send

Dario

cdj wrote: lots of time i see strange chars in serial output

I know nothing about Esp8266, but be aware that interrupts occurring during transmission can affect the serial data.
About adding transistors, I doubt it could be a solution in that case. They are slow and act as inverters.
[Edit]
Oh, I just see that you're referring to that guide , so your are talking about level shifter between a 5V powered Arduino and the 3.3V Esp8266. In that case the transistors are used as follower and they do not invert the signal but I'm not sure that 2N2222 is the best choice for .