I have had the same prob many time...massive lactic acid build up cutting my sets short. especially on low dose EQ, the lactic build up and pump is unbareable. Partially due to all the abuse my lungs took in the 90's and not being able to deliver the neccessary amount of oxygen to my muscles=rapid lactic acid build up.
I have experimented with everything to combat this.
The most sucessful for me is
1)TUMS (or also baking soda mixed into pre-workout drink or any sodium bicarbonate powder) 30% to my rep #'s on only tums...crazy. Before the burn stopped me short of max reps. Its an interesting feeling not having lactic acid build up, cause you want to keep going til you feel it....be careful, thats is how Ive gotten injured. ...An excercise physiology professor at my university said that "blood ph" is regulated closely and any bicarb would be counter acted in 5-10 minutes or so BUT the tums or baking soda has a noticable effect for at least 30-40 minutes for me. Upon further discussion with this professor, he stated that 'Cellular ph' is very different from 'Blood Ph' and is regualted in a different manner.
2)AAKG (beta alanine and norvaline help also)
3)Promagnon aka pmag or hroid depending on company selling it (4hydroxy methyl test precursor...not to be confused with the "1,4 ene" 'hdrol' among other names (basically the 4hydroxy boldenone precursor). Takes away the lactate build up so much that I can do reps for daaaaays. more than most orals (along with superdrol) to the point where Ive injured my shoulder a few times "overdoing it"....the lactic acid helps me to realize its time to stop and rest a few minutes.
also, its true that your body uses lactic acid as energy during anaerobic atp production, but its the LACTATE portion of the 'lactic acid ' molecule that is used. the Acid portion (hydrogen ion actually), once separated from the lactate portion, is what causes the burn...BUT BUT BUT, that burn is the trigger for a host of physiologic actions (i.e. peptide hormone release: GH, IGF-1, Prostaglandins etc..amongst other things) that are a part of the muscle building/"adaptation" process. I always tell people "inflamation is part of what triggers the rebuilding process".
So for that reason I also avoid NSAID's when possible.