Allow me to chime in here:
MAFT in blow thru allows you to vent the Tial-type(not hks-type) BOV to the atmosphere, rather than suck-thru, which risks closed-throttle stalling issues.
The basic MAFT will allow you to pair any size injectors with the engine, rather than being restriced to 550's, like a Lexus combo requires.If your goals are ~300hp, you will be fine with the basic MAFT.
Some people will piggyback an Apexi into the Maft to add that finer tuning element, but it really isn't necessary. The MAFT is adjustable(fuel-wise) all across the rpm range. It doesn't have the point-by-point resolution of other units, but it'll interpolate those rpm points just fine.
The downpipe is indeed seperated, but as mentioned, would probably benefit from a small tab in between the two holes to further isolate the exhaust gases from one another.
The bolt in the lower section is there for a wideband O2 sensor. The exhaust setup is quite quiet with the silencer in place, due to it having a second muffler at midpoint.
The HKS filter element should indeed be replaced on a regular basis. The element in there is probably due for this now. Overall, you should be able to get about 260hp with just 8psi.
Expect about 290 around 12psi.
How do I know? Because those were my parts you bought, and that's what they got me.
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