Dear all members,
I found the problem that makes my code works slower than his. It's just only few instructions that I added in (these instructions have nothing related to any loops, it just checks the port bit for the configuration). Here is a part of my code that works:

 
MAIN:	ACALL PRESET		; Call Preset routine

CONFIG:	JNB P4.6,REVDUAL	; Detect WOCT config bit
	CLR IEN1.5		; Disable Timer2 CM1 interrupt
	ACALL WOCT		; Call WOCT routine

REVDUAL:JNB P1.1,DUAL		; Detect DUAL config bit

FA:	JNB P1.3,FB		; Detect FWD_A enable cmd
	JB P0.4,AON		; If A firing cmd on, jump to AON
        JB P3.5,REG		; If Voltage still high, jump to REG
	CLR P0.5		; Turn B firing cmd off
	CLR P1.2		; Turn Regen signal off
	MOV CMH0,#18H		; Load CMH0 with 18H
        MOV CML0,#00H		; Load CML0 with 00H
	ACALL DELAY		; 50ms
	SETB TCON.4		; Start TM0
ADUAL:	SETB P0.4		; Turn A firing cmd on
AON:	JBC 20H.0,CTRLA		; Test CT0 done bit flag
	AJMP CHECK1		; /

CTRLA:	AJMP FWD_C		; FWD_C control routine
								
FB:	JNB P1.4,REG		; Detect REV_B enable cmd
	JB P0.5,BON		; If B firing cmd on, jump to 
        JB P3.7,REG		; If voltage still high, jump to REG
        CLR P0.4		; Turn A firing cmd off
	CLR P1.2		; Turn Regen signal off
	MOV CMH1,#18H		; Reload CMH1 with 18H
	MOV CML1,#00H		; Reload CML1 with 00H
	ACALL DELAY		; 50ms
	SETB TCON.4		; Start TM0
BDUAL:	SETB P0.5		; Turn B firing cmd on
BON:	JBC 20H.0,CTRLB		; Test CT0 done bit flag
	AJMP CHECK3		; /
	
CTRLB:	AJMP REV_C		; REV_C control routine

This is the segment of code which caused problem:
Please notice those lines in bold
<pre>
MAIN: ACALL PRESET ; Call Preset routine

CONFIG: JNB P4.6,REVDUAL ; Detect WOCT config bit
CLR IEN1.5 ; Disable Timer2 CM1 interrupt
ACALL WOCT ; Call WOCT routine

REVDUAL:JNB P1.1,DUAL ; Detect DUAL config bit

FA: JNB P1.3,FB ; Detect FWD_A enable cmd
JB P0.4,AON ; If A firing cmd on, jump to AON
JB P3.5,REG ; If Voltage still high, jump to REG
JNB P4.6,NOCT ; Test the WOCT config bit
CLR P0.5 ; Turn B firing cmd off
NOCT: CLR P1.2 ; Turn Regen signal off
MOV CMH0,#18H ; Load CMH0 with 18H
MOV CML0,#00H ; Load CML0 with 00H
ACALL DELAY ; 50ms
SETB TCON.4 ; Start TM0
ADUAL: SETB P0.4 ; Turn A firing cmd on
AON: JBC 20H.0,CTRLA ; Test CT0 done bit flag
AJMP CHECK1 ; /

CTRLA: AJMP FWD_C ; FWD_C control routine

FB: JNB P1.4,REG ; Detect REV_B enable cmd
JB P0.5,BON ; If B firing cmd on, jump to
JB P3.7,REG ; If voltage still high, jump to REG
CLR P0.4 ; Turn A firing cmd off
CLR P1.2 ; Turn Regen signal off
MOV CMH1,#18H ; Reload CMH1 with 18H
MOV CML1,#00H ; Reload CML1 with 00H
ACALL DELAY ; 50ms
SETB TCON.4 ; Start TM0
BDUAL: SETB P0.5 ; Turn B firing cmd on
BON: JNB P1.3,AOFF ; Detect FWD_A enable cmd
BCON: JBC 20H.0,CTRLB ; Test CT0 done bit flag
AJMP CHECK3 ; /

AOFF: CLR P0.4 ; Turn A firing cmd off
JMP BCON ; Jump back to BCON

CTRLB: AJMP REV_C ; REV_C control routine

It's so insignificant but somehow it affects the perfomance of the unit which causes something that I couldn't understand. Right now I can't upload the waveforms of my Tektronic 720PA scope here, but I will try later. It bothers me for a while but I don't know what it is. Hope you will shed me some light to this matter.
Thank you all for your attention.

Regard,
T.L