Can not figure this one out:

Bought my 98 Blazer on site a year ago... looked clean, 155k miles, but clean. Drove around the parking lot, all seemed well, 4x4 etc... Bought and paid for it.
Pulled out of parking lot and mashed on the gas... absolutely nothing. I was scared the transmission was failing, could barely get the truck up to 30 mph.
Anyways, had the CAT cut off, no difference. Had magnaflow replacement put back in so I would not get codes.
In the process of doing a tune up, I changed the fuel filter and one spark plug. Don't remember why, but got in and decided to test drive then... mashed on the gas and it came alive, I was amazed. So i'm sure it was a very clogged fuel filter.
Finished other 5 plugs and wires, cap and rotor, air filter, pcv valve.
To the average person... it runs great. But to me, it does not have the low end power it should. I had a 96 with same mileage years ago and I could spin tires just by mashing on the gas.
This 98 that I have now.. only way to spin a tire is mash on it going around a corner. Trying to be funny at my brothers house with my 98. couldn't spin a tire at all in his driveway. foot on brakes and full throttle.
Anyways, my goal is not to do burnouts, I'm just referencing to the difference in low end power. The 98 runs great, starts very quickly, has a very slight vibration at idle, but overall runs great. I've cleaned the EGR. No codes in computer.

Also after doing the fuel filter I changed the fuel pump, original was squealling very loud. figured easier to do now before it leaves me straded.

Any suggestions to why I feel my truck lacks in low end power. I guess I need to go drive another one to compare it to, but I found this forum and figured I'd see what you guys said.

I used to be impressed with the vortec motors, kinda peppy...

Any suggestions would be awesome.