Howdy
I have a 1986 blazer with NA 6.2 milspec. at 60K miles I installed stans long tube headers with open exhaust. I also made a larger airfilter housing and ram air system and cleaned up and matched the intake to the heads. I have an amsoil 6inch racing air filter.
The seat-o-the-pants meter was marginal, definitely an improvement but nothing drastic.
By FAR the best improvement I did to this truck was at 90k miles I had the pump and injectors rebuilt to modern specs. All the injectors were bench matched and the pump was increased by 1/4 turn per the shop that I use for all my pump work. This yielded a very noticeable difference in performance. The only time I see black smoke is when I pull a load or really get my foot into it, and even then it's not bad.
If I had done this at the same time as the headers, it would have been a huge improvement over the existing specs.
All that said, my sons ATS turbo 6.2 will still blow my doors off....BUT nothing, and mean NOTHING, sounds as sweet as a NA diesel at around 2500 with headers! I am lucky I work with all the local cops....
Another thing you might want to do is pull the heads and clean them up and replace the gaskets with newer style fel-pros.
Hope this helps!
1996 Chvy 3500 CCDWLB 6.5 Heathed, NO vac, marine injctrs, ARB bumper, BIG pipe, 3" lift, bright lights, bypass oil system.
1986 Chvy 6.2 M1009 blazer RAM AIR, Headers, Custom interior
2001 Chinook RV, V10 gas
1974 John Deere 1530 diesel tractor
1993 John Deere 455 Diesel lawn mower
1967 GTO, 1989 Honda Transalp
2009 VW Jetta TDI, flashed and piped, 6speed, fun car!
1998 6.5 suburban, stock, daughter's
1993 6.5 3500 CCSWLB GM8, Heathed, big exhaust, gauges, Son's
1984 6.2 ATS turbo 3500, SCDWLB - Son's
3 kids, 1 wife, 1 dog
Gunsmith, Tactics Instructor, Fabricator USMC 87-93 Semper Fi!