tc_sj There are a couple of easy things to do if you are looking for a couple more mph.
#1 remove the windshield and go with either a comp shield or full face helmet
#2 tape up any seams along the hood.
#3 enclose the passenger side of the car and tape down the tonno cover
#4 air pressure in the tires max, put nitrogen in them also for high speed runs.
#5 As you said check the rev limiter in the car, may need to add 500 rpm.
#6 EXHAUST, the biggest killer of power. Race pipes are needed.
#7 drop the nose of the car about 1" for wedge to help push through the air.
#8 Fill in the radiator openning with aluminum or wood to stop the air from getting under the car and lifting at high speeds. Same with front ducts in nose.
These 8 things should get you into the 150 club with what you have.
Unless you have a full certified rollcage, fire suit, and other safety equipment in the car, You should be happy with the 145.
I have been to 135mph and was happy with this. Have been to 158 mph in 1/4 mile and it was not alot of fun when things don't go just right. Front end lift off from the wind coming at you from the end of the track. Did need to change shorts after run. No damage but what a ride.
Rick L.