What next for routine?

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So i been a hard gainer my whole life. Was floating around 145-155 no matter how much i ate or what i did in gym. Turns out i think i was over training so i plateaud... Anyways i figured that out, dialed in my diet and workout till i got to about 160 lean. Than had a chance to do a cycle (i know i didnt get my natural potential) After the loss of water weight i was 168 lean and my str was up. Now i been natural for about 4 months going hard doing a 5 day split over 10 days. NOw im 180. Not as lean as i perfer but im gaining and my strength going up. I am currently doing HIIT training from dorian yates "blood and guts". And im wondering when i should switch it up? and what is a good routine to do for bulk after that kind of workout. Prior to that i would do like pyramid sets going like 12,10,8,6,6,6 first few being warmup. Should i do high volume to switch it up? or stick to low reps / high weight type routines, like possibly 5x5 or something. Thanks. And i plan on going natural to about 190 than ill do another cycle.