I have a 2010 GT auto with the small Roush M90 blower. The oem upper grille is 80% blocked off. (mostly closed off honeycombs + upper foglamps, black pony dead center, etc).
I tossed the oem upper grille and replaced it with the 7 bar upper grille....(mounts in 6 places). This 7 bar upper grille mod also eliminates the upper foglamps. Forget who made it at the time, but also installed the offset top radiator cover. That too puts more air through the upper portion of the Roush HE. The HE on the 2010 Roush PD blowers is full sized, both top to bottom, and also left to right. The same HE on the M90 is also used on the bigger Roush TVS-2300 blower setups.
With the 7 bar upper grille, the upper portion of the Roush HE gets way more air through it. It also eliminates the 2 x 90 deg bends into the ...'snorkel' that feeds the oem airbox. With the oem upper grille, you can't even see the 'snorkel'. With the 7 bar upper grille installed, airflow is now straight into the 'snorkel' and a slight increase in boost results.
I don't get any high speed front end lift....even at 137 mph. The 2010 cars came with an undertray that goes all the way back to the engine, and then some. It has to be removed to access the eng oil filter. Also installed the CDC lower grille, which puts more airflow through the lower grille. (the CDC lower grille also has the option for front brake cooling, so in went the 14" dust shields + 2.5" silicone hoses from new lower grille to dust shields. No more brake stink). The CDC lower grille slides in on top of the oem lower grille, and is angled downwards. Front end of car was lowered 1". (it's now only 1/2"). Eng was lowered 1/4" via the steeda eng mounts. Ceramic coated JBA LT's (catted H) put the new cats below the front seats, oem cats were at the base of the eng bay. Ok, no more eng bay heat issues. Eng bay temps dropped 40F (measured).
The poor 5R55S auto tranny would go from 170F to 200F in mere seconds on the hwy with blower on. So in went the B+M auto tranny cooler (bar+ plate type), and mounted directly below the oem Ford auto tranny cooler (tube + fin type). The 2 x auto tranny coolers are plumbed in series. On the 2010, the auto tranny coolers are sandwiched between the eng rad and the AC rad. Both tranny coolers are only 3/4" thick. The Roush HE is huge, and sits in front of everything... including the power steering rad. Ok, now auto tranny temps with blower on, increases to 171 F....and sometime 172F...problem solved. Previous to that, I installed the PA deeper pan on the 5R55S, which is very thick, and ribbed aluminum...and holds an extra 4 qts of auto tranny fluid. Also had installed the JDM catch can for the 5R55S...neither mod reduced temps. The fix was the 2nd auto tranny rad.
Point here is, with the extra large auto tranny cooler + Roush HE (+ eng rad, AC rad, power steering rad), you need a lot of air through the entire mess to be effective. I have a total of 6 x rads to get air through.
Talk to any of the road course folks. They either remove the oem upper grill entirely or replace it with the 9 bar grille (05-09 cars) or 7 bar grille on the 2010. The 13/14 GT-500's don't even have an upper grille.
