B737-700 CREW WAS ISSUED THE COWBY RNAV ONE SID. THE CTLR THEN TOLD THE CREW THEY WERE CLRED TO A WAYPOINT ON DIFFERENT RNAV SID. WHEN PASSING 7300 FT AT A HIGH RATE OF CLB; THE CTLR ISSUED MAINTAIN 8000 FT.

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PRIOR TO DEP; THE CAPT AND I REVIEWED THE COWBY1-GUP DEP PROC; GIVEN IN THE CLRNC; IN DETAIL; DISCUSSED THE RESTRS; LNAV/RNAV PROCS; AND THE NOTES ON THE WX PACKET CONCERNING ALTS AT LAS. DEPARTED LAS ON THE COWBY1-GUP. LAS DEP CLRED FLT TO FL190 UNRESTR AFTER RBELL; AND PRIOR TO ROPPR. AFTER ROPPR; DEP CLRED US TO FORGE (NOT ON DEP PROC). I COULDN'T FIND FORGE ON THE SID OR IN THE FMC AND ASKED CTLR TO CLARIFY FIX. AGAIN CLRED TO FORGE (ON THE TRALR1 SID); AND I STILL COULDN'T IDENT THE FIX. BEFORE FURTHER CLARIFICATION COULD BE INITIATED; AND PASSING 7000 FT IN THE CLB TO FL190; CTLR GAVE US A L TURN TO HEADING 140 DEGS AND MAINTAIN 8000 FT. THE CAPT IMMEDIATELY REDUCED THE PWR TO IDLE; REDUCED THE PITCH AND BEGAN THE TURN. THE ENSUING INERTIA CAUSED THE ACFT TO CLB TO 8300 FT AND THE AIRSPD TO ACCELERATE TO APPROX 267 KIAS. ONCE ACFT PARAMETERS WERE REESTABLISHED ON THE HEADING OF 140 DEGS; 8000 FT; AND 250 KIAS; THE CTLR RESPONDED THAT HE HAD CLRED US TO THE WRONG FIX; FOLLOWED BY A CLRNC TO COWBY. HOWEVER; WHEN GIVEN AN ALT TO MAINTAIN WITH LESS THAN 1000 FT OF WARNING; HEADING CHANGE; AND MY HEAD IN THE COCKPIT LOOKING FOR A FIX NOT ON THE SID; THIS CREATED THE CIRCUMSTANCES LEADING TO THE ALT/AIRSPD DEV. EVEN IF I HAD NOT BEEN HEAD DOWN IN THE COCKPIT; THE CAPT COULD NOT HAVE RESPONDED ANY QUICKER OR MORE APPROPRIATELY TO PREVENT THE DEV. POSSIBLY THE CAPT OR I SHOULD HAVE RESPONDED TO THE 8000 FT CLRNC WITH 'UNABLE' WHILE ARRESTING THE CLB. THE CTLRS SHOULD BE; AND I'M SURE MOST ARE; AWARE OF THE RATE OF CLB OF OUR ACFT; AND THE INERTIA WHEN CLBING UNRESTR AT LOW ALTS. WITH THE MULTITUDE OF SIDS/STARS AT LAS; I CAN UNDERSTAND A CTLR MAKING THIS TYPE OF ERROR. I DO BELIEVE THERE ARE ENTIRELY TOO MANY PROCS AT LAS; AND THIS IN ITSELF CAUSES MANY OF THE VIOLATIONS/DEVS.