Evo5madness

Just had cold air box put in my evo 5, 8 motor. Also just had cosworth head gasket and studs installed. Was driving along and car was running sweet as. Then as I started to accelerate it started dicking around. As though getting no air. Oil pressure good, revs where not changing, temp good. Just wouldnt accelerate. Checked all intercooler lines and no hoses off. At a bit of a loss. I can nana it to 100km/hr but if I was to try to accelerate harder it just misses. Also struggles to idle. Help